THE INFLUENCE OF NITRIC OXIDE ON PHYSICAL EFFORT CAPACITY AND OXIDATIVE STRESS
Giurgea N., Constantinescu M. I., Suciu S., Dorofteiu, M., Stanciu, R.
Numerous studies support the implication of nitric oxide (NO) in diverse physiological processes but there are few accounts of the influence of NO in physical exercise capacity (POC). There is though a well-documented correlation between NO metabolism and reactive oxygen species production (ROS). We investigated the influence of NO on POC of adult rats, through administration of L-arginine and methylen blue, a precursor and an antagonist of NO activity, respectively, and we measured its effects through quantification of two reliable oxidative stress markers, that is, malondialdehide (MDA) and ceruloplasmine. We used a pretest-postest experimental design according to which we preliminary measured the POC of 24 adult Wistar rats. The animals were thereafter injected intravenous (i.v.) either with L-arginine (n = 12; 300 mg/kg) or methylen blue (n = 12; 0.3 mg/kg). Two hours after the experimental manipulation, we quantified again the POC of rats, using the data from pretest as control for comparison. We dosed the level of glucose, proteins, lipids, MDA, and ceruloplasmine from blood. Our results indicated that L-arginine determines a significant reduction of both distance, and duration of physical effort, correlated with significant reductions of glucose and protein levels. Only when associated with physical exercise L-arginine determines a significant reduction of MDA and ceruloplasmine concentrations. In contrast, methylen blue increases the POC of rats, associated with non-significant metabolic modications, but with a significant reduction of MDA concentration, and a significant increase of ceruloplasmine concentration. These results led us to conclude that NO reduces PEC, possibly acting as a ROS scavenger, although its participation as a reactive form of O2 to muscular fatigue cannot be definitely excluded. Methylen blue increases PEC along with antioxidant activity, probably through a different mechanism.
Department of Physiology, Iuliu Hatieganu University of Medicine and Pharmacy, Cluj-Napoca, 3400 CJ, Romania
EFFECTS OF WEAK ELECTROMAGNETIC FIELD ON CUTANEOUS VASOMOTOR RESPONSES
Tretjakovs P., Jurka A., Stefanovska A., Aivars J., Pirags V.
The purpose of our study was to evaluate by means of laser Doppler fluxmetry (LDF) the effect of weak electromagnetic field (wEF) on cutaneous vasomotor activity. The subjects were 22 diabetic patients (D) without late diabetic micro- or macro-vascular complications and 20 healthy volunteers as controls (C). The groups were matched for age, sex, and body mass index.We recorded cutaneous blood flow and changes in the flow induced by wEF (0.9+/-0.6 mT, 80+/-34 Hz, 60 min) by alfa-PULSAR (Electronic Ltd) on the pulp and on the dorsum of the big toe using LDF (PeriFlux 4001, Perimed). We evaluated changes in the dynamics of the LDF signal by spectral analysis (SA) based on wavelet transformation. The vasoconstrictor response to deep inspiration was measured (on the pulp) before and after 60 min of wEF. The results showed a significant increase in LDF maximum compared with resting LDF on the dorsum in both groups (D, p<0.05; C, p<0.0001), but on the pulp - only in the control group (p<0.001). On the dorsum, the data of SP showed an increase in the mean amplitude of oscillations of LDF in the frequency interval from 0.009 to 2.3 Hz compared to values at rest (D, p<0.01; C, p<0.001). Comparing the mean amplitude from 0.009 to 0.018 Hz (reflect metabolic activities), an increase was only in controls on the pulp (p<0.05). After 60 min of wEF influence, the vasoconstrictor response to deep inspiration increased in both groups (p<0.05 and p<0.001), but the effect was lower in the diabetic group compared to the control group (p<0.001). In conclusion, our findings indicate that wEF induces functional alterations (endothelial vasoactive production), which can improve circulatory performance. The alterations in metabolic activity due to wEF may improve control of the autonomic sympathetic neurovascular system in diabetic patients.
University of Latvia, Riga, Latvia
SEASONAL TESTICULAR CYCLE IN MERIONES SHAWI (GERBILLIDAE). EFFECTS OF TEMPERATURE AND PHOTOPERIOD.
Sellami A., Maurel D., Siaud Ph.
Seasonal reproductive cycle of male gerbils, Meriones shawi shawi (desert rodent, Gerbillidae) was determined in animals reared under natural temperature and photoperiod conditions. There was no statistically significant variation in plasma testosterone values measured monthly during the eighteen months of experiment. Testis volume reached a maximum in spring and summer. Minimal values occurred during November-December, in the colder months and in short photoperiod (winter solstice).
The effect of cold temperature (1 month at 10°C) on testicular activity in animals maintained at 25°C before and after this "cold experiment" was investigated. There was no statistically significant variation in plasma testosterone values measured during these cold or hot temperature conditions. After the 10°C period the testis volume was found to be decrease and come back to normal values when brought back to 25°C.
The effect of photoperiod, short days (8L:16D) versus long days (16L:8D) was studied. There was no statistically significant difference between plasma testosterone values measured in animals stabulated in short days and in long days. The testis volume increased in animals maintained in long days compared to animals maintained in short days.
These observations show an apparent dissociation between exocrine and endocrine testicular activity in this species. This species exhibits a constant endocrine activity through the whole year. On the other hand, the testis volume (more representative of the exocrine activity) appears dependent on the photoperiodic and thermic conditions.
Labo. Physio. an., Fac. Sciences, Tunis, Tunisie; Lab. Otologie, EPI 9902, UER Médecine Nord, Marseille, France
POLYMORPHISM OF THE ROD VISUAL PIGMENT BETWEEN ALLOPATRIC POPULATIONS OF THE SAND GOBY
Donner K., Jokela M., Vartio A., Fyhrquist-Vanni N., Paulin L., Merilä J.
The rod visual pigments of four populations of sand goby (Pomatoschistus minutus) living in spectrally different light environments were studied by micro-
spectrophotometry and opsin sequencing in a quest for adaptive differences within the same species. The populations were that of the Baltic Sea at the
SW coast of Finland (maximal transmission of the water 550-575 nm), Kattegat at the west coast of Sweden (500-550 nm), the English Channel at
Plymouth (500-525 nm) and the Adriatic Sea near Venice (450-475 nm). Small but statistically significant differences between the absorbance maxima of
the rhodopsins (varying from 508.3 nm in the Baltic to 503.0 nm in the Adriatic population) correlated with the differences in the light environment
(except in the English vs. the Swedish population). Opsin gene sequences were compared, on one hand, to reveal functional amino acid substitutions
that may underlie the spectral differences, on the other hand to be related to cytochrome B phylogeny.
University of Helsinki, Helsinki, Finland
COPPER ZINC SOD IN ANEMONIA VIRIDIS, AN ANIMAL SUBMITTED TO DAILY HYPEROXIC CONDITIONS
Plantivaux A., Richier S., Merle P.-L., Furla P., Garello G., Zoccola D., Tambutté S., Tambutté E., Allemand D.
Animal tissues submitted to hyperoxic environment usually display severe damage, mainly due to radical oxygen species (ROS) overproduction. However, some animals, such as sea anemones and corals, are adapted to hyperoxic conditions. These animals harbor symbiotic protists, named zooxanthellae, which possess photosynthetic capacities. Using O2 microelectrodes implanted within the sea anemone Anemonia viridis (cnidarians), we confirmed that, under light condition, zooxanthellae rapidly photosynthesize oxygen at levels toxic for many cells (3-times normoxia). In these conditions, no apparent tissue damage occurs, suggesting that these animals are good models to study ROS detoxifying strategies. Moreover, the symbiosis is sometimes disrupted, leading to a phenomenon called bleaching, responsible for massive worldwide cnidarian death episodes. Although the cellular signaling remains to be identified, it has been proposed that ROS could play important roles in the processes leading to bleaching. This explains why the study of ROS detoxification in these cells is also of environmental interest.
We focused our interest on superoxide dismutases (SOD), which are the first actors of the ROS enzymatic defenses. Using native-gel electrophoresis and inhibitors, a great variety of SOD was distinguished in Anemonia viridis: CuZn, Mn and also Fe SOD, with a specific tissue distribution. We further characterized CuZnSOD, which activity appeared restricted to animal tissues. By a molecular approach, two CuZnSOD isoforms were cloned (AY164663 & AY164664), having 40% of homology and distinct 5' regions. Using in situ hybridization, we confirmed that both CuZnSOD transcripts were immunolocalized in animal tissues, but not in zooxanthellae.
These results are a first step toward the understanding of the mechanisms of resistance against oxidative stress in the partners of this particular symbiosis.
UMR ROSE, U. Nice Sophia-Antipolis, F-06108 Nice, FRANCE & Centre Scientifique de Mocaco MC-98000
CARDIAC ADAPTATIONS IN THE TIME COURSE OF AN ALTITUDE TRAINING CAMP IN A RAT MODEL
Reboul C., Tanguy S., Oudet N., Melin A., Juan J.M., Dauzat M., Obert P.
Introduction : Recent studies have reported controversial results on the ability of altitude training to induce increase in aerobic performances in athletes. Although cardiovascular system is playing a key role in aerobic performances, there are very few reports on cardiac morphological and functional adaptations following altitude training, and conflicting results have been found. The aim of this study was to investigate the cardiac modifications induced by 5 weeks aerobic training at altitude.
Methods : Twenty six rats were randomly assigned to 3 groups : N (n=9, living in normoxia, 80 m, PIO2= 159 mmHg), NT (n=9, living and training in normoxia, 80 m, PIO2= 159 mmHg) and CHT (living and training in hypoxia, 2800 m, PIO2= 105 mmHg). CHT and NT were subjected to the same relative training endurance program for 5 weeks (45 min per day, 80% maximal aerobic velocity, 5 days per week). Morphological and functional cardiac parameters were evaluated by Doppler-echocardiograhy, catheterization and aortic pulsed-Doppler transducer.
Results : In CHT group, the main findings were a right ventricular hypertrophy [right ventricular mass: (CHT)=130±14.7 mg/100g and (NT)=118±11.8 mg/100g; p<0.05] associated with a reduced pulmonary right ventricular flow peak velocity [(CHT)=58±7 cm/s and (NT)=74.9 cm/s; p<0.001]. Moreover trained rats, CHT and NT presented a concentric and eccentric left ventricular hypertrophy respectively (NT and CHT versus N; p<0.01). However, the resulting increase in systemic cardiac output (Qc) remains lower in CHT rats when compared to NT [(CHT)=16±2 ml/min/100g and (NT)=18±2 ml/min/100g; p<0.05].
Conclusion : Our results suggest that both training and hypoxia could induce changes in loading conditions, leading to the specific cardiac adaptations reported here. Moreover, those modifications suggest that cardiovascular system could, in part, directly be involved in the limitation of the beneficial effects of altitude training.
Laboratoire DICV, Laboratoire de Physiologie des Adaptations Cardiovasculaires à l'exercice, Avignon - FRANCE
MUSCLE AND BRAIN OXYGENATION DURING EXHAUSTIVE CYCLING IN THE CIRRHOTIC PATIENT
Bay Nielsen H., Henry Secher N., Ott P.
In cirrhotic patients exercise capacity is reduced and we hypothesised that the hyperdynamic splanchnic circulation induces insufficiently elevated or even reduced O2 availability of muscle and brain as evaluated by near-infrared spectrophotometry (NIRS). Eight cirrhotic patients underwent semi-supine cycling at light (29 ± 3 W, mean with SEM), moderate (57 ± 5 W) and exhaustive (84 ± 11 W) intensities for 10 min each. Arterial and hepatic venous blood blood samples were obtained and also hepatosplanchnic (HSP) blood flow was determined using constant infusion of indocyanione green. Resting heart rate and mean arterial pressure were 70 ± 4 b/min and 89 ± 2 mmHg, respectively, and they increased to 140 ± 6 b/min and 117 ± 4 mmHg, respectively, during exhaustive exercise. Cardiac output increased from 6 ± 1 to 14 ± 1 l/min, while HSP became reduced (from 1.0 ± 0.1 l/min to 0.7 ± 0.1 l/min). Arterial lactate reached 2.7± 0.6 mmol/l compared to 0.3 ± 0.1 mmol/l at rest with enhanced HSP lactate uptake (0.3 ± 0.1 vs. 1.4 ± 0.2 mmol/min) and glucose output (0.6 ± 0.1 vs. 1.5 ± 0.2 mmol/min) during cycling. Cerebral oxygenation increased from 67 ± 6% to 71 ± 4% during exercise. An elevated concentration of oxygenated and deoxygenated hemoglobin of muscle during exercise reflect that muscle blood flow more than compensated for an increase in O2 extraction. The results suggest a cellular impairment rather than an attenuated availability of substrate and O2 to muscle and brain during exercise in the cirrhotic patient.
Dept. Hepatology and Anesthesiology, Rigshospitalet, Univ. of Copenhagen - Denmark
ELECTROENCEPHALOGRAM IN CHILDREN WITH DIABETES MELLITUS
Sfredel V., Trăilă A., Iancu I., Dănoiu S. Matcas H., Sfredel D.
Objectives. The purpose of this study was to find the relation between diabetes mellitus (DM) at children and the electroencephalogram (EEG) changes, the correlation between these changes and the stage of this disease or the number of the severe hypoglycemic attacks.
Material and methods. The standard EEG was obtained from 15 children with DM, mean age 15.2 years, 5 boys and 10 girls. Patients were randomized in two groups by the criteria stage of DM and the number of the severe hypoglycemic attacks (convulsions). We have also recorded EEG at 15 normal children, same mean age and sex.
We have analyzed the basic parameters of EEG (amplitude, frequency, index), the placement of the alpha and beta waves and the lesional and irritative waves.
Results. Discussions. The analyze of the results took into account the specific of the EEG in children and specially the high index of irritative waves. We found 38.4 % children with convulsive hypoglycemic attacks and a high correlation between these attacks and the historic of DM.
The standard EEG was normal at 40,5 % of patients. 55 % of patients reveal a high index of unspecify irritative waves (spikes, polyspikes, slowly, hypervoltated waves), most of them syncronisated, bilateral and unsistematised. We also recorded a relative high index of slowly waves in theta and delta bands, with a mean voltage. In 54.5 % patients we found a positive correlation between the changes of EEG and the number and the severity of the hypoglycemic attacks.
Conclusions. 55 % of the children with DM reveal changes of EEG in different degrees of severity in correlation with the historic of DM or the number of convulsivante hypoglycemic attacks.
University of Medicine and Pharmacy Craiova - Department of Physiology and Pathophysiology, Roumania
SERUM LEPTIN, INSULIN AND CORTISOL LEVELS AFTER A SUBMAXIMAL EXERCISE IN SEDENTARY AND TRAINED MEN
Zaouali Ajina M., Bouassida Chikhaoui A., Charfeddine B., Miled A., Gharbi N., Tabka Z., Zbidi A.
The aim of this study is to determine the effect of a submaximal exercise and recovery on leptin, cortisol and insulin levels.
The experimental protocol consists in a submaximal exercise on 2 sessions of 21min each 70% maximal oxygen uptake (VO2 max) for the first exercise and to 85% VO2 max for the second exercise separated by a passive recovery period (40 minutes) or active recovery at 30% of VO2max. Blood samples are taking before and after every session and after 2 hours and 24 hours of recovery period.
After a submaximal exercise of 21 minutes leptin concentration doesn’t change for either sedentary or trained subjects. After 2 hours of recovery, a significant decrease in two groups is noted compared to the value of the end of the first session. There’s a significant difference on leptin level between the two groups at all steps and during the two protocols. The sedentary presents more elevated leptin values that those of trained men.
The cortisol level increases significantly of 21,5 % at the sedentary following the first session of the exercise. However, a is noted after 2 hours of recovery compared to the end of first session. No remarkable difference is noted between the two groups concerning cortisol level either in protocol with passive or active recovery. A significant reduction of 52% at the sedentary in insulin level is found at the end of the first session of exercise. This value is re-establishes at the end of the passive recovery. However, a significant reduction is also noted at the end of the second session and remains after 2 hours of recovery to reach after 24 hours a value that is not different of the basis value. No significant difference is noted between the sedentary and trained subjects in two protocols.
Leptin responses to submaximal exercise appears therefore during recovery period and precisely after 2 hours and its during this period that appears the effect of other regulating hormones as insulin and cortisol.
Service De Physiologie Et Des Explorations Fonctionnelles Faculte De Medecine. Sousse. Tunisie
IL-1b EXPRESSION AND SECRETION BY HUMAN ORAL EPITHELIAL CELLS IN RESPONSE TO C. ALBICANS INFECTION
Mostefaoui Y., Claveau I., Rouabhia M.
Oropharyngeal candidiases are the most common form of mucosal fungal infections and are primarily caused by Candida albicans, a dimorphic fungal commensal organism of the gastrointestinal tract. Clinical and experimental observations suggest that, through cytokines and chemokines, oral epithelial cells play key role in host defense against candidiasis. In this context we sought to investigate whether oral epithelial cells convey IL-1b as a pro-inflammatory cytokine against C. albicans infection. To reach our goal, we engineered human oral mucosa, and then infected the tissue with live or dead C. albicans (10ex5 yeast/cm2). At the end of each appropriate contact period, we measured the expression of IL-1b at the mRNA and protein level. We also evaluated the effect of the tissue on C. albicans adherence and growth. Only live C. albicans modulate IL-1b expression and secretion. In deed, our results showed that IL-1b mRNA expression was significantly increased at early infection stage, and then deceased at later infective phase. The modulatory effect of C. albicans on IL-1b expression was confirmed by an increased amount of inactive form (33 kDa) of IL-1b at early infection period and significant decrease at subsequent contact periods. When active form (17 kDa) was measured in the supernatant, it showed a significant and time dependent increase of IL-1b secreted by epithelial cells infected with live C. albicans. These results indicate that IL-1b is involved in the local defense against C. albicans infection. On the other hand, we showed that oral epithelial cells down-regulate the growth of live C. albicans. Taken together, these results provide additional evidence for the contribution of oral epithelial cells to local defenses against exogenous stimulation such as C. albicans infection. (Funded by the FRSQ, NSERC and CIHR).
Faculté de médecine dentaire/GREB, Université Laval, Quebec, Canada G1K-7P4
S4 Blood pressure regulation
RENAL SODIUM HANDLING AND BLOOD PRESSURE CONTROL
The association between dietary sodium intake and blood pressure and its cardiovascular complications has been recognized for several decades. The evidence that sodium plays an important pathophysiological role in the development of hypertension comes from various sources including epidemiological, physiological and pathophysiological studies. The recent report of the molecular mechanisms involved in the pathogenesis of some rare forms of hypertension with a simple Mendelian inheritance pattern, i.e the Liddle’s syndrome, the glucocorticoid-remediable hypertension and the apparent mineralocorticoid excess (AME) has revived the interest for salt-induced hypertension since the reported genetic defects decrease the ability of the kidneys to excrete sodium. Whether the same mechanisms apply for highly prevalent forms of essential hypertension is still unknown but it is very likely that other mechanisms contribute to the increase in blood pressure in essential hypertension. In fact, there is also increasing experimental and clinical evidence that an increased sodium reabsorption in the renal proximal tubule could contribute to the development of hypertension. Using lithium clearance as a marker of renal sodium handling by the proximal tubule, we have demonstrated in rats as well as in humans that hypertension is associated with an impaired modulation of sodium excretion in the proximal tubule. More recently, we have also found that sodium handling by the proximal tubule is an independent determinant of the sensitivity of blood pressure to salt in hypertension. The development of new molecular techniques and possibly also new physiological tools to investigate in greater details the renal response to sodium should offer the opportunity to revisit the still partly puzzling association of salt and blood pressure.
Division of Hypertension and Vascular Medicine, Lausanne, Switzerland
COMPARATIVE PHYSIOLOGY OF THE CARDIOVASCULAR SYSTEM
Westerhof N. (1), Segers P. (2), Stergiopulos N. (3)
Blood pressure and Cardiac Output, result from the interaction of heart, including venous return, and arterial system. Using simple descriptions of heart and arterial load we can quantitatively describe how pressure and flow arise. We then derive ventriculo-arterial coupling parameters and compare them in different mammals.
The heart is described by the varying elastance model. Parameters: slopes of the diastolic (Emin) and end-systolic (Emax) pressure-volume relations, and their intercept with the volume axis (Vd). Ventricular filling pressure is Pv. The arterial load is modeled with the 3-element windkessel model: peripheral resistance (R), arterial compliance (C) and aortic characteristic impedance (Zc), with RC = τ the time constant of diastolic aortic pressure decay. This overall model allows evaluation of the contribution of the individual parameters to pressure and flow. Application of dimensional analysis leads to nondimensional ventriculo-arterial coupling parameters: τ/T and CEmax.
Comparative physiology makes use of the allometric equation: P = P0 Me, with P the parameter of concern (reference value P0), M body mass, and e exponent. A double logarithmic plot of T and τ, against body mass shows that the ratio of τ/T is similar in all mammals. Since PP/Pmean = τ/T it follows that with similar mean pressure also pulse pressure is the same in mammals. An analogous reasoning holds for CEmax. The ratio of characteristic impedance and peripheral resistance is similar in mammals too. This implies that systemic arterial input impedance, when normalized, is similar in mammals, suggesting similar shapes of pressure and flow waves. While pressures are similar, Cardiac Output and whole body metabolism are proportional to body mass (i.e., exponent e = 1).
We conclude that comparative physiology of cardiovascular parameters explains the similarity in pressure and flow wave shapes.
(1)Laboratory for Physiology, Institute for Cardiovascular Research, Vrije Universiteit Amsterdam, The Netherlands; (2)Hydraulics Laboratory, Institute of Biomedical Technology, University of Gent, Belgium; (3)Biomedical Engineering Laboratory, EPFL, Lausanne Switzerland.
PROTECTION OF HEART FROM REPERFUSION INJURY BY THE MITOCHONDRIAL PERMEABILITY TRANSITION INHIBITORS
Sagach V., Shymanskaya T., Nadtochiy S.
Last years it have been shown the postreperfusion disturbances of cardiac contractility will be due to the different metabolites that release from mitochondria under an opening of mitochondrial permeability transition pore. These agents effect on heart function and vessels tone. In experiments on isolated hearts of guinea-pigs, perfused under Langendorff preparation, possible protection of hearts from reperfusion injury by the known inhibitors of mitochondria permeability transition pore - cyclosporin A, and trolox - water-soluble vitamin E - was studied. It has been shown that cardiac reperfusion was followed with an increase in an oxygen cost of myocardial work by 83% from control level in 40 min of reperfusion, in addition to the disturbances of cardiac contractility, tone of the coronary vessels and heart rate. The heart and oxygen metabolism disturbances, stimulated by global 20 min ischaemia and reperfusion, were significantly decreased by a preliminary application of investigated agents. Trolox improved cardiac recovery both when it was perfused in vitro and after its administration per os before the heart removing. In this case in 40 min of heart reperfusion left ventricular developed pressure was 79% as compared to 51% in that at control; dР/dtmax and dР/dtmin by 88% and 85% accordingly against 66% and 45% in control; oxygen cost of myocardial work didn`t change reliably. Conclusion: postreperfusion disturbances of cardiac contractility, tone of the coronary vessels and heart rate, as well as noneffective oxygen utilization by the heart tissue were due to an opening of mitochondrial permeability transition pore. Cyclosporin A and trolox protected the heart from reperfusion disturbances.
Bogomolets Institute of Physiology, Department of Blood Circulation, Kiev, Ukraine
ANP HINDERS POST IMMERSION VASOMOTOR ADJUSTMENTS
Mourot L., Wolf J.P., Robinet C., Galland F., Bouhaddi M., Courtiere A., Meliet J.L., Regnard J.
Changes in vasomotor tone and hemodynamics were compared before and after dehydration linked and not to water immersion. 10 highly fit divers underwent two similar 6 h exposures (periods of alternate rest and exercise) performed in a dry ambience (DY) and, 4 weeks later, with immersion up to the neck in 15°C water (WI). Venous blood was taken thirty minutes before and after each exposure, to assess hematocrit (Hct), hemoglobine (Hb), plasma concentration of total proteins and vasomotor agents: noradrenaline (NA), arginin vasopressine (AVP) and atrial natriuretic factor (ANF). Heart rate (HR), stroke volume (SV; cardiac impedance), systolic (SAP), diastolic (DAP), and mean (MAP) arterial pressures were also measured. Htc and Hb were used to estimate changes in plasma volume (PV) and to correct plasma concentration of vasoactive mediators. Total peripheral resistance (TPR) was calculated as the ratio of MAP/CO (cardiac output). Weight loss was similar after both WI and DY (mean 2.4 kg; p<0.05 with baseline on each day) but PV reduction was greater after WI than DY (-14.7 ± 1.6 % and -9.7 ± 1.6 %; p<0.05). CO and MAP were maintained, but HR was reduced only after DY (p<0.05) whereas SV was reduced only after WI (p = 0.07). Vasoconstrictor agents were released (p<0.05) in both dehydration conditions with NA and AVP higher (p<0.01) after WI than DY. After DY, DAP (NS) and TPR (p<0.05) were increased, but not after WI. Thus, dehydration prompted the release of vasoconstrictor mediators. After DY, CO was maintained with an increased TPR, triggering in turn a baroreflex decreased HR. Conversely, within one hour after WI a marked trend to SV decrease was present, but HR and TPR were unchanged despite the twofold larger increase in plasma vasoconstrictor mediators than after DY. We submit that the amount of ANF released during WI impeded the action of NA and AVP, causing in turn the supine unchanged arterial pressures and TPR.
Laboratoire de Physiologie Médecine BESANCON, Institut de Médecine Navale du Service de Santé des Armées TOULON, FRANCE
DETERIORATION IN CAROTID BAROREFLEX DURING CAROTID ENDARTERECTOMY
Sigaudo-Roussel D., Evans DH., Naylor AR., Panerai RB., London NL., Bell P., Gaunt ME.
Blood pressure instability after carotid endarterectomy (CEA) has been associated with a disturbance of the baroreflex control mechanism caused by the surgery on the carotid sinus region. The purpose of this study was to identify if a deterioration in carotid baroreceptors occurs during the surgery. Heart rate (HR) and blood pressure (BP) were recorded continuously in 60 patients undergoing CEA as well as pre-operatively and post-operatively at 2 days and 6 weeks. The baroreflex sensitivity was determined by cross-spectral analysis of HR and SBP. During the surgery, three tests were used to assess the baroreflex response. The first test simulated a sudden fall in systemic blood pressure by clamping the common carotid artery. The second test simulated a rise in systemic blood pressure by applying a pressure using a rubbing action on the luminal surface of the carotid sinus region. The rub test was performed twice, once with the atheromatous plaque in situ and once when the plaque had been removed. The third test is the clamp removal and restoration of blood flow through the carotid sinus. Carotid cross-clamping increased systolic blood pressure (SBP) from 117±3 mmHg before clamping to 125±3 mmHg (P<0.05) at 30 beats after clamping. The first rub test with the plaque in situ decreased SBP from 121±3 mmHg to 117±3 mmHg (P<0.01) at 10 beats after the rub test, indicating a functioning baroreceptor reflex. The second rub test increased SBP from 126±3 mmHg to 128±3 mmHg, (P<0.05). SBP dropped (p<0.01) when unclamping suggesting a selective alteration of the baroreflex sensitivity. The baroreflex sensitivity was significantly reduced 2 days post-operatively than pre-operatively (P<0.05). These findings suggest that the act of plaque removal could be associated with a partial disruption of baroreceptor mechanism in the carotid artery. This could affect type I baroreceptors.
Department of Medical Physics and Surgery, LRI, Leicester, UNITED KINGDOM and Laboratory of Physiology, Medecine school, ANGERS, FRANCE
MECHANISMS OF ACETYLCHOLINE AND FLOW-INDUCED VASODILATATION IN MESENTERIC ARTERY
Lopez V., Thorsgaard M., Buus NH., Simonsen U.
The purpose of the present study was to investigate whether endothelium-dependent vasodilatation evoked by acetylcholine and flow is mediated by the same mechanisms in isolated rat mesenteric small arteries. Mesenteric small arteries were mounted in a pressure-myograph for the measurement of internal diameter. The segments were stretched to 110% of passive length and pressure kept at 80 mmHg. Vessels were contracted with the tromboxane analogue, U46619 (10-7M) and flow was applied by a peristaltic pump resulting in shear stress levels of 4 and 16 dyn/cm2. Indomethacin was present throughout the experiment. In endothelium-intact vessels low (5.1±0.6 dynes/cm2) and high (19±2 dynes/cm2) shear stress evoked vasodilatations which were reduced by endothelial cell removal, 68±11 and 68±8% respectively (P<0.05, n=7), while acetylcholine vasodilatation was abolished. A nitric oxide synthase inhibitor, asymmetric dimethylarginine (ADMA, 1 mM), reduced low and high shear stress-evoked vasodilatation, but it did not change acetylcholine-evoked vasorelaxation. Inhibition of Ca2+-activated K+ channels with the combination of apamin (0.5*10-6M) and charybdotoxin (0.1*10-6M) did not change shear stress and acetylcholine-evoked vasodilatation, but in combination with ADMA, they abolished acetylcholine-evoked vasodilatations while shear stress-induced vasodilatation was unaltered. The presence of an Src tyrosine kinase inhibitor, herbimycin A (10-6M) had no effect on acetylcholine vasodilatations, but it abolished low and high shear stress-evoked vasodilatation, respectively, 32±12 and 68±14% (P<0.05, n=8). The present study suggests that Ca2+-activated K+ channels are involved in acetylcholine–evoked vasodilatation, while a Src tyrosine kinase is involved in flow-induced nitric oxide (NO)-mediated vasodilatation in rat mesenteric small arteries.
Depart. Pharmacology, University of Aarhus,8000 Aarhus C, Denmark
CONTRIBUTION OF NO-SYNTHASE AND ARGINASE TO MEDULLARY CARDIOVASCULAR CONTROL IN RATS
Shapoval L.N., Sagach V.F., Pobegailo L.S., Dmytrenko O.V.
In acute experiments on anaesthetized normotensive and spontaneously hypertensive rats we attempted to analyze the contribution of neuronal NO-synthase (nNOS) and arginase to the activity of the cardiovascular neurons within the medulla oblongata. Unilateral injections of both L-arginine, substrate for NO synthesis, and NO donor sodium nitroprusside into the medullary cardiovascular nuclei (NTS, DVN, AMB, LRN) in most experiments resulted in lowering the SAP level mainly due to reducing the peripheral vascular resistance. Their effects were more pronounced in spontaneously hypertensive rats as compared to normotensive ones. The data obtained give evidence for an uneven distribution of NO-producing neurons within the medulla in dorso-ventral direction. Preliminary inhibiting nNOS with 7-nitroindazol attenuated the haemodynamic responses on L-arginine injections into the medullary structures. Injections of either nNOS inhibitor L-NNA or antagonist for arginase norvaline into the medullary nuclei induced mainly an elevation of the SAP which was similar in both normotensive and spontaneously hypertensive rats. Both enzymes are known to use L-arginine as a substrate for their metabolism, so they can compete for it in some cases. Distribution of arginase- containing neurons within the medulla oblongata seems to be also uneven and corresponds to that of NO-producing ones. We suggest that arginase participates in the mechanisms of the central cardiovascular control together with nNOS perhaps modulating the activity of nNOS
Bogomoletz Institute of Physiology National Acad.Sci, Kyiv, Ukraine
PHYSIOLOGICAL AND METABOLICAL STUDIES OF HYPERTHYROID RAT HEART
Revnic C.R., Revnic F., Botea S., Voiculescu V.
Introduction: A better understanding of action mechanisms of Thyroid hormone on peripherial vascularisation is essential for the recognising T3 as a therapeutic agent.The aim of our study was to investigates the effect of T3 administred in excess on physiological and biochemical parameters of rat myocardium Material and methods:16 Wistar rats have received injections with T3 4.5 mg/kg body weight for four weeks.The hearts has been mounted in Langendorf retrograde perfussion using Krebs Hanseleit buffer for 30 minutes followed by 60 minutes reperfussion. Heart rate,coronary flow and left ventricle developed pressure have been recorded at the end of stabilisation period and during reperfussion in order to see the heart capacity to recover after a medium ishemia. Biochemical parameters:LDH,CK,SOD,CT,LDL and HDL fractions ,total lipids and lipid peroxides have been determined using standard methods.Results: During reperfusion,cardiac frequency is unchanged while LVPD is very much amplified and coronary flow exibits a decrease in its values in hyperthiroid hearts comparatively with contols. There is an increase in myocardium and plasma CK and LDH is four times higher than in contols, accounting for the increase in anaerobic glycolisis.A decrease in SOD in hyperthiroid myocardium accaunts for the onset of oxidative stressTotal lipids are significantly increased serving as energetic support for accelerated metabolism Conclusion: Following a medium ischemia hyperthiroid heart has a good capacity to recover ,the only modified parameter is LVDP which is very much amplified. Due to low plasma cholesterol levels and of the absence of a significant modification of plasma lipid peroxides ,hyperthiroid rats are not the target for atherogenic factors which are present in other forms of arterial hypertension.
UMF"Carol Davila",*NIGG"Ana Aslan",*V.Babes Institute,Bucharest,Romania
GENETICS OF FAMILIAL HYPERKALAEMIC HYPERTENSION
Delaloy C., Hachouel J., Jeunemaitre X.
Familial Hyperkalaemic Hypertension (FHH), also called Gordon’s syndrome or pseudohypoaldosteronism type II, is a rare mendelian autosomal dominant form of hypertension associating hyperkalaemia, low renin and aldosterone plasma levels. The study of a large family from the North of France showed no strong relationship between the severity of the metabolic disorders and blood pressure, which exhibited a positive relation with age as in the normal population. Affected patients are very sensitive to small doses of thiazide diuretics. FHH is the mirror image of Gitelman’s syndrome, caused by mutations in the thiazide-sensitive sodium-chloride cotransporter (NCC). In addition to phenotypic heterogeneity, genetic heterogeneity has been demonstrated. Three loci have been identified at 1q, 17q and 12p, and there is evidence for of at least a fourth locus.
The first two genes found as responsible for the disease, WNK1 and WNK4, belong to a new family of serine-threonine kinases. The causing-disease mutations in WNK4 are missense mutations clustering in highly conserved domains close to the coiled-coil domains. The mutations in WNK1 are large deletions in intron 1, which could increase the expression of the gene. The regulation of WNK1 expression is complex with at least two isoforms, expressed ubiquitously or specifically in the kidney (mainly in the distal tubule). The two kinases are localized either in the cytoplasm (WNK1) or at the tight junctions (WNK4) of the distal tubular cells where they could increase sodium reabsorption by a mechanism that might involve an increase of NCC activity and/or chloride transport through tight junctions. A decrease of NCC-mediated sodium flux by WNK4 has recently been demonstrated in Xenopus oocytes, while WNK1 prevented WNK4 inhibition of this transporter. These results could explain the positive effects of WNK4 mutations or increased expression of WNK1 on sodium transport in the distal tubule.
INSERM U36, Collège de France, Paris, France
INTERACTIONS BETWEEN POSITIVE AND NEGATIVE FEEDBACK IN THE REGULATION OF BLOOD PRESSURE
The neural regulation of arterial blood pressure is traditionally attributed to the interaction of two main mechanisms: central integration and peripheral negative feedback reflexes. Numerous experimental observations, however, have clearly demonstrated the existence of peripheral cardiovascular reflexes, usually mediated by sympathetic afferent fibers (Rev Physiol Biochem Pharmacol 1982; 94: 11-74), that are unequivocally excitatory in nature. For instance, it has been demonstrated that the distension of a short segment of the thoracic descending aorta, i.e. a stimulus mimicking the effects on aortic wall of an increase in pressure, induces a reflex pressor response through a sympathetic excitatory reflex initiated by aortic receptors (Circ Res 1974; 34: 78-84 and 1982; 50: 125-132). Accordingly, the existence of positive feedback reflex mechanisms was proposed. Furthermore, during the stretch of the thoracic aorta the gain of the reflex bradycardia response to an increase in arterial pressure was markedly blunted. On the other hand it is well-known that quadriplegic patients can undergo marked hypertensive crises during gentle stimulation of the abdomen. The new scheme of neural regulation of arterial pressure that we have been proposing during the last two decades is based on the continuous interaction of three mechanisms: 1) central integration, 2) peripheral negative feedback and 3) peripheral positive feedback reflex mechanisms. The interaction of opposing principles, besides being a fundamental biological property, would ensure a more adequate control of cardiovascular variables in terms of stability and different velocities of changes (i.e. instability) according to the various behavioral needs. Finally, the excitatory cardiovascular reflexes mediated by sympathetic afferents may become particularly important in several pathophysiological conditions of paramount importance (Hypertension 2002; 39: 63-68).
Dipartimento di Scienze Cliniche "Luigi Sacco" - Ospedale Sacco - Università degli Studi - Milano - Italy
BIPHASIC EFFECTS OF ANGIOTENSIN (1-7) AND ITS INTERACTIONS WITH ANGIOTENSIN II IN RAT AORTA
Haulica I., Bild W., Mihaila CN., Ionita T., Boisteanu CP., Neagu B.
Objective: to investigate the effects and possible relationship between ang (1-7) and angiotensin II at the vascular level.
Method: Experiments were performed on isolated rat aortic rings perfused with Krebs-Henseleit saline, using isometric force transducers.
Results: Angiotensin (1-7) induced well-known endothelium-dependent relaxation and vasodilating effects in preparations precontracted with phenylephrine. Without preconstriction, angiotensin (1-7) in high doses (10-6 – 10-5 M) produced either a significant inhibition of angiotensin II vasoconstriction or a nontachyphylaxis vasopressor response. While losartan (a selective AT1 receptor antagonist) inhibited the vasoconstriction induced by angiotensin (1-7), A779 (a selective ang (1-7) receptor antagonist) blocked only its relaxation. Unlike losartan, blockade of AT2 receptors with PD 123319 remained without effect.
Conclusion: Taking into account the biphasic effects of angiotensin (1-7), we proposed that it is one of the active components of the renin-angiotensin system, which is involved as a modulator both in the counter-regulatory actions of angiotensin II and in the self-regulation of its own vasodilating effects.
Laboratory of Experimental and Applied Physiology of the Romanian Academy – Iasi, Romania
ANTIHYPERTENSIVE AND DIURETIC EFFECTS OF THE LEAF EXTRACT OF ANNONA MURICATA (ANNONACEAE) IN RAT.
Dimo T., Mbuyo Pami E., Nguelefack T. B., Panjo Yewah M., Njamen D., Talla E.
In Cameroon, concoctions of Annona mirucata leaves are used in the treatment of arterial hypertension by traditionnal healers. The antihypertensive effects of the methanol extract of A. muricata leaves were evaluated in normotensive Wistar rats (NTR) and Salt-Loaded Hypertensive Rats (SLHR) using the direct cannulation method. Acute changes in urine volume and urinary excretion of Na+ and K+ were also studied. Intravenous administration of the extract induced a significant dose-dependent fall in mean arterial blood pressure (MABP). At the lowest dose of 5 mg/kg, the extract reduced MABP in NTR and SLHR by 27% and 34%, respectively. At 50 mg/kg, decreases of 37% and 53% were obtained in NTR and SLHR, respectively. The antihypertensive effect of the extract was more remarkable in hypertensive than in normotensive rats. A. muricata did not provoke significant changes in urine volume and excretion of Na+ and K+ in NTR at the dose of 150 mg/kg. Oral administration of the extract at 300 mg/kg, resulted in a significant increase in urinary volume in NTR and SLHR by 76% and 201%, respectively. Urinary excretion of Na+ was increased by 804% in SLHR, whereas change in K+ excretion was not significant. The extract of A. muricata is thus a promising source of antihypertensive and diuretic pharmaceuticals.
University of Yaounde I - Cameroon
EFFECTS OF METOPROLOL ON ISCHAEMIA-INDUCED “COMPENSATORY” FLOW CHANGES IN ANAESTHETISED DOGS
Ványi J., Papp J.Gy., Parratt J.R., Végh Á.
In anaesthetised dogs occlusion of one of the main branches of the left coronary artery results in an increase in blood flow through the other main branch of the same artery. The underlying mechanisms of this "compensatory" flow increase occurring within the normal, non-ischaemic area are not known. In the present study we examined whether b1-adrenoceptors, which are present in both the myocytes and large coronary arteries in this species, are involved in this phenomenon. In 10 chloralose-urethane anaesthetised dogs ischaemia was induced by four 5 min occlusions of the left anterior descending coronary artery (LAD) with 10 min reperfusion intervals between the occlusions. One hour later, the selective b1-receptor antagonist metoprolol was infused in a dose of 1 mg kg-1min-1 in a side branch of the LAD, 20 min prior to, and then throughout, the repeated occlusion / reperfusion cycles. Coronary blood flow was measured both on the LAD and the circumflex (LCX) coronary arteries by Doppler and electromagnetic flow probes, respectively. Coronary flow reserve was assessed as the maximum increase in flow velocity following increasing doses of intracoronary adenosine (from 12.5 to 200 mg). LAD occlusions resulted in significant increases in diastolic blood flow in the LCX (of 24 ± 3, 23 ± 3, 23 ± 3 and 22 ± 4 ml min-1 during occlusions 1-4 respectively). These "compensatory" flow increases
were significantly attenuated to 9 ± 2, 10 ± 1, 8 ± 1 and 9 ± 2 ml min-1 (P < 0,05) when the occlusions were repeated in the presence of metoprolol. Metoprolol did not modify baseline coronary flows in either artery nor did it modify the hyperaemic coronary flow velocity changes which resulted either from reperfusion or adenosine administration. Since metoprolol was, at least in part, able to reduce the "compensatory" flow increase we conclude that catecholamines might play a role in this phenomenon. However, metoprolol did not influence coronary flow reserve.
Gottsegen National Institute of Cardiology and Dept of Pharmacology – Budapest, Hungary
THE EFFECT OF ESTROGEN REPLACEMENT THERAPY ON ACCUMULATION OF FOAM CELLS IN DIABETIC MALE RABBIT
Sharifi A., Sharifi M., Fesharaki M., Allai H.
The risk factors for cardiovascular diseases are related directly or indirectly in men as in women, to lipid and lipoproteins plasma level. But women have the advantage of the beneficial effects of either endogenous or exogenous estrogen on these levels throughout most of their lives. Disease such as diabetes interfere with the favourable lipids and lipoproteins plasma levels seen in men, and heart disease risk is significantly increased. The aim of this project is to study the effect of estrogen on accumulation of foam cells, cholesterol, triglyceride, Low Density Lipoprotein, High Density Lipoprotein, in diabetic male rabbits. Diabetes was induced in 21 male white rabbits by injecting alloxan (200mg/kg) into the lateral air vein. Diabetic rabbits were divided in to three groups and were given nutrition as following: 1- high cholesterol diet, 2-high cholesterol diet +estrogen (1mg/rabbit/week), 3-high cholesterol diet + estrogen (5 mg/rabbit/week). Their blood sample was taken before and after of the study and the plasma level of cholesterol, triglyceride, HDL, LDL, and was measured. Blood pressure was measured directly in all groups of experimental animals. The cholesterol, LDL and accumulation of fatty streak reduce in groups that received estrogen (p<.05). HDL in group three is lower than group two(p>.05). Triglyceride in group two and three is lower than group one (p>.05). Data have been shown mean ± standard error and for comparison of interagroups used T-paired-test and ANOVA for comparison intergroups. The P<.05 is significant.
It seems that estrogen with high and low dose can reduce cholesterol, LDL, triglyceride and accumulation of foam cells in diabetic animal as well as non-diabetic one. Estrogen inhibits HDL reduction and does not change triglyceride value. According to this research estrogen replacement therapy is suggested, but more study is needed to confirm the absolute effect.
Medical University of Kurdistan - Sanandaj - IRAN