Department of Anaesthesiology and Intensive Care, University Hospital Center and Group A.R.R.E, University of Rennes, Rennes, France

AIM:Exercise training is known to improve endothelium-dependent relaxation in the coronary and skeletal muscle arteries. However, the effects of exercise training on peripheral nonworking tissue, including microcirculation, are still unclear. Therefore, we investigated the effect of chronic and regular aerobic exercise on cutaneous microvascular endothelial function in rats.METHODS:We assessed the effect of physical training on skin microcirculation in 7 sedentary (SED) and 21 training rats (Wistar-Kyoto), submitted to a treadmill training protocol (15 m/min; 15% incline; 60 min/day; 8 weeks). Training rats were divided into 3 groups, exercising 1 day/week (Ex1), 3 days/week (Ex3) or 5 days/week (Ex5). Cutaneous blood flow was recorded before the beginning of the training protocol, after 4 weeks and at the end of the training program. Hyperemic response (RH) was the flow reaction obtained after sudden release of the garrot. For data analysis, cutaneous vascular conductance (CVC) was indexed as cutaneous blood flow divided by mean arterial blood pressure (in millimeters of mercury, mmHg) and normalized to baseline values.RESULTS:At baseline, CVC was not different among groups (SED or training) at 3 steps of experimental protocol. The hyperemic stimulus significantly increased normalized CVC only in group Ex3 after 4 weeks (P<0.006) and 8 weeks (P<0.006).CONCLUSION:Exercise training exerts a generalized effect on the vasculature by increasing endothelial function in vessel beds different from those perfusing actively working muscle. However, some differences exist since training at a frequency of 3 bouts weekly only modifies cutaneous microcirculation.

OBJECTIVES:We report in the present study the role of endothelin (ET-1) and ET-1 receptors in the sustained hypoxia-induced systemic hypertension. METHODS:Wistar rats were randomly assigned to live continuously in hypobaric hypoxia (CH rats) or normoxia (N rats). At the end of hypoxic stress exposure (5 weeks at 450 mm Hg), measurements of mean systemic arterial pressure were done. The effects of ET-1 in the presence or not of the endothelium and/or of specific ET-A inhibitors (BQ-123) or ET-B inhibitors (BQ-788), have been investigated in an isolated model of rat thoracic aorta. Finally, plasmatic ET-1 concentrations have been determined by assay procedure. RESULTS:Following five weeks of chronic hypoxic stress, CH rats presented a significant increase of mean systemic arterial pressure (N: 129.1+/-6.8 mm Hg vs CH: 152.5+/-3.4 mm Hg; P<0.05). Despite of this hypoxia-induced hypertension, ET-1 plasmatic concentration was not different between N and CH rats. Finally, CH rats presented a reduce response to ET-1 when compared to N rats. This phenomenon seems to be associated to the ET-A vascular smooth muscle cell receptors, since difference between N and CH rats was still present in endothelium denuded aortic rings in the presence or not of the specific ET-B inhibitors (BQ-788). In addition, in the presence of the specific ET-A inhibitor (BQ-123) response to ET-1 was abolished in N and CH rats to the same extent (N:-98%; CH:-99%). CONCLUSION:This work clearly suggests that, following long term exposure to hypoxia, ET-1 and ET-1 receptors are not involved in the persistence of systemic hypertension in a rat model, and that chronic exposure to severe hypoxic stress was associated with a downregulation of the ET-A receptors response to ET-1.

We undertook this study to determine whether long-term high intensity exercise would modify cutaneous endothelial-dependent vasodilation. We compared a group of 9 highly trained windsurfers (mean age: 24.5 +/- 1.6 years) to a control group of 8 sedentary individuals (22.9 +/- 0.4 years, NS). Laser Doppler was used to measure cutaneous blood flow in the resting state (baseline), during post-occlusive hyperaemia (endothelium-dependent vasodilation), and local heating to 42 degrees C. Lipid profile was similar in both groups. Resting heart rate was significantly lower in windsurfers. Baseline cutaneous vascular conductance (CVC) values were similar in both groups (0.059 +/- 0.016 and 0.051 +/- 0.009). During reactive hyperaemia, normalized peak CVC value was significantly higher in the windsurfers group (1775.4 +/- 286.9 and 826.4 +/- 121.7 % baseline CVC; p = 0.01). Normalized peak CVC value in response to local heating (42 degrees C) was not significantly different between both groups (2359.4 +/- 346.1 and 1467.7 +/- 282.6 % baseline CVC). Endothelium-dependent vasodilation in cutaneous microcirculation is significantly enhanced in the forearm skin of highly trained windsurfers when compared to sedentary controls.

Les decouvertes des mecanismes regulateurs du diametre des vaisseaux via des facteurs endotheliaux de relaxation (monoxyde d'azote - NO°-, prostacycline, EDHF) et de contraction (endotheline, thromboxane A2, angiotensine II, ATP-ADP, UTP, anion superoxyde) ont revele le role majeur de l'endothelium dans le controle de la vasomotricite. La fonction endotheliale peut etre evaluee chez l'homme par de nombreuses methodes et techniques : plethysmographie, doppler pulse ou continu avec injection d'acetylcholine ou augmentation de flux de perfusion, detections seriques du NO°, de l'endotheline, de l'A II permettant de connaitre l'importance d'un eventuel dysfonctionnement endothelial au niveau de differents territoires vasculaires. La fonction endotheliale peut etre alteree dans certaines pathologies humaines, comme dans l'hypertension arterielle ou l'insuffisance cardiaque mais aussi au cours du vieillissement. Face a ces dysfonctionnements endotheliaux, le clinicien dispose de differentes demarches therapeutiques. La premiere est non medicamenteuse, preventive, mais aussi curative : la pratique d'une activite physique moderee: en effet, l'exercice potentialise les mecanismes vasodilatateurs endothelium-dependant (avec augmentation de la production de NO° et parfois de prostacycline). Il faut ajouter a cela une consommation faible d'alcool et l'abstinence au tabac (inducteurs de dysfonctionnements endotheliaux). Les autres demarches proviennent d'une palette de nombreux agents phannacologiques dont seulement quelques molecules sont deja utilisees pour « traiter » le dysfonctionnement endothelial et d'autres parmi lesquelles les chercheurs et les cliniciens ont l'espoir de voir se developper des molecules prometteuses.

Alkylglycerols are natural etherlipids abundant in shark liver oil (SLO) in a diacylated form. SLO is known to have antitumor properties and was recently described as an inhibitor of tumor neovascularization. However, most studies did not discriminate between the respective activities of alkylglycerols and of fatty acids, which both have potent biological properties. In this work, a mouse model was used to investigate the antitumor effects of SLO and of alkylglycerols purified from the same source, both administered orally. We demonstrated that either pure alkylglycerols or SLO reduced the tumor growth in a similar manner suggesting that alkylglycerols were involved in this effect. In alkylglycerol-treated mice, metastasis dissemination was reduced by 64 +/- 8%, whereas SLO effect was 30 +/- 9% below control. Purified alkylglycerols also decreased significantly plasmalogen content in tumors, whereas SLO had no such effect. Finally, we demonstrated that a 5-day treatment with alkylglycerols curtailed the presence in tumors of von Willebrand factor a marker of endothelial cells. This result suggested an anti-angiogenic effect of alkylglycerols. In summary, alkylglycerols were shown to decrease the growth, vascularization, and dissemination of Lewis lung carcinoma tumors in mice. These findings suggest that the antitumor activity of SLO is likely mediated by the presence of alkylglycerols.

Regulation of endothelial barrier function often occurs through signalling involving phospholipase C activation which produces diacylglycerol (DAG), a lipidic second messenger activator of protein kinase C (PKC). Therefore, modification of lipidic composition of endothelial cell membranes might modify DAG production and, as a result, alter regulation of endothelial permeability. We investigated the in vitro effects of natural 1-O-alkylglycerols on porcine aortic endothelial cell permeability to dye-labelled albumin. [3H]-1-O-alkylglycerols (10 microm) were substantially incorporated into phosphatidylcholine (6.6%) and phosphatidylethanolamine (4.4%). Stimulation of endothelial cell monolayer with phorbol-myristate-acetate or with the calcium ionophore A23187 resulted in a raise in permeability to albumin. Pre-treatment with 1-O-alkylglycerols (10 microm, 24 h) had no effect on basal albumin permeability but totally inhibited the effect of phorbol-myristate-acetate, and brought the permeability of A23187-stimulated endothelial cell monolayers below control. After incubation of cells with [3H]-1-O-alkylglycerols (10 microm, 24 h), we detected the production of the analogue of DAG, and PKC inhibitor, [3H]-1-O-alkyl-2-acyl-glycerol, in resting cells. This production was increased by 58% under A23187 stimulation while phorbol-myristate-acetate had no effect. Our data demonstrate that natural 1-O-alkylglycerols modify endothelial permeability, and suggest that this effect could be mediated through alteration of lipidic signalling.

The erectile function of the corpus cavernosum is a balance between smooth muscle contraction and relaxation modulated by nerve terminals and endothelial cells1. It is clearly demonstrated that the mechanisms of erection and detumescence are not exclusively modulated by cholinergic and adrenergic nerves but also by non-adrenergic, non-cholinergic (NANC) neuromodulators2. Purines (particularly ATP, ADP) are present in the environment of endothelial cells and smooth muscle cells of the corpus cavernosum. Nevertheless, the implication of P2y and P2x purinoceptors respectively in tumescence and detumescence have not studied before in man.

Although the neurobiological causative factors are now beginning to be understood, to a large extent the complex mechanisms involved in migraine remain an enigma, with the appearance of a transient unilateral cephalic pain, possibly preceded by a protean aura and associated with several other symptoms. The factors involved include three clinical signs or symptoms, i.e., pain, the aura (focalized neurological and neurosensory signs), and accompanying symptoms (e.g., sensory, psychological, or digestive); and three anatomical sites, i.e., the brain, the meningeal or intracranial vessel and a peripheral cranial nerve, the trigeminus (V). Familial hemiplegic migraine (FHM) has led to a consideration of the genetic origin of ionic channel-dependent pathologies (channelopathies), while certain other arguments which are for the most part indirect favor the hypothesis of abnormalities, again possibly of genetic origin, in the central neurotransmitters (including serotonin), which are involved in the transmission of pain messages and in vasomotor control. However, the main point is that each of the sites involved has its specific pharmacopoeia, which can contribute towards the treatment of migraine.

Although the neurobiological causative factors are now beginning to be understood, to a large extent the complex mechanisms involved in migraine remain an enigma, with the appearance of a transient unilateral cephalic pain, possibly preceded by a protean aura and associated with several other symptoms. The factors involved include three clinical signs or symptoms, ie., pain, the aura (focalized neurological and neurosensory signs), and accompanying symptoms (e.g., sensory, psychological, or digestive); and three anatomical sites, i.e., the brain, the meningeal or intracranial vessel and a peripheral cranial nerve, the trigeminus (V). Familial hemiplegic migraine (FHM) has led to a consideration of the genetic origin of ionic channel-dependent pathologies (channelopathies), while certain other arguments which are for the most part indirect favor the hypothesis of abnormalities, again possibly of genetic origin, in the central neurotransmitters (including serotonin), which are involved in the transmission of pain messages and in vasomotor control. However, the main point is that each of the sites involved has its specific pharmacopoeia, which can contribute towards the treatment of migraine. (C) 2000 Editions scientifiques et medicales Elsevier SAS.

We conducted two parallel studies on cryopreserved arterial homografts: a biomechanical study based on traction tests and a functional study coupled with a histology examination. Twenty-four arterial segments from 6 donors (2 iliac and 2 superficial femoral segments per donor) were cryopreserved at -150 degrees C and -80 degrees C. Cryopreservation lasted at least 6 months. Lengthening at rupture, the Young elasticity module, and rupture stress were calculated from the traction test. Results were significantly different depending on the preservation temperature. The functional properties of the cryopreserved arterial grafts were evaluated by studying the vasomotricity capacity of the vascular smooth muscle (VSM) and the endothelium. The expected results (direct contracture of VSM induced by PHE and endothelial dependent relaxation of VSM induced by ACH) were measured on fresh arteries. Cryopreserved arteries showed no response to physiological doses of PHE and ACH, whatever the preservation temperature. In one-third of the cases, a lower amplitude vasoconstriction was obtained using nonphysiological doses of PHE; there was no relaxation with ACH.

Endothelial cells were isolated from bovine thoracic aorta and cultured. Bovine aortic endothelial cells (BAEC) were incubated with radiolabeled arachidonic acid (3H-AA) or eicosapentaenoic acid (14C-EPA) (1 microM) for 3 hr. Both fatty acids were predominantly incorporated into phosphatidylcholine (57 +/- 2% and 62 +/- 2% respectively) and slightly into phosphatidylethanolamine (11 +/- 0.5% and 12 +/- 0.6% respectively). phosphatidylinositol (26 +/- 1.5% and 10 +/- 0.5% respectively) and neutral lipids (6 +/- 0.5% and 15 +/- 1% respectively). After BAEC incubation with 3H-AA for 24 hr with or without EPA (1 microM), the release of radioactive metabolites of AA induced by thrombin (5.5 U/ml) was strongly reduced by the preliminary treatment with EPA (72 +/- 5%). After BAEC incubation with AA, EPA or vehicle (control), endothelin-1 levels were measured by RIA in the culture medium and we observed that: 1) the basal production of endothelin-1 was not modified after either AA or EPA treatment, 2) the thrombin-evoked release of endothelin-1 was significantly reduced by EPA (5.8 +/- 0.82 and 3.8 +/- 0.50 pg/microg proteins in control and EPA-treated cells, respectively); 3) by contrast, AA had no significant effect on the thrombin-evoked release of endothelin-1. In conclusion, EPA reduces strongly the endothelin-1 release but AA is ineffective. This reduction of endothelin-1 release may account partly for some of the vascular effects of EPA.

The effects of adrenomedullin were evaluated in isolated vascular rings from rats treated with monocrotaline (60 mg/kg, s.c.) causing pulmonary hypertension and right ventricular hypertrophy within 3 to 4 weeks. Sham animals (NaCl-treated rats) were used for comparison. The relaxing effects of adrenomedullin (10(-8) M) and acetylcholine (10(-6) M) were determined in thoracic aorta and pulmonary artery rings precontracted with phenylephrine (10(-7) M). In sham animals, adrenomedullin caused significant vasorelaxation of aorta and pulmonary artery although of different amplitude (24 +/- 3% and 40 +/- 2%, respectively). A greater relaxation was observed in response to acetylcholine. Monocrotaline-treated rats exhibited a reduction in adrenomedullin relaxation in pulmonary artery (54 and 68% loss of effect, at 3 and 4 weeks, respectively, P < 0.01 vs. sham) and comparable reductions in acetylcholine responses. The decrease in adrenomedullin relaxing effect was less pronounced in aorta than in pulmonary artery, suggesting a distinct tissue sensitivity to monocrotaline. In contrast, the relaxing effect of acetylcholine on aorta was decreased at 4 weeks (36% reduction, P < 0.01 vs. sham). In this model, the adrenomedullin-induced relaxation of the pulmonary artery was impaired due to a severe endothelial dysfunction which may contribute partly to the evolving pathophysiological process.

PURPOSE:Endothelial P2y purinoceptor stimulation is known to induce vasodilatation mediated by NO release from endothelial cells. We examined the effect of a potent P2y agonist, adenosine-5'-O-(2-thiodiphosphate) (ADPbetaS), on human corporal cavernosal strips and its dependence on a functional endothelial lining. MATERIALS AND METHODS:The preparations mounted in isometric conditions were precontracted by noradrenaline (NA) at a concentration of 0.1 microM. Increasing concentrations of ADPbetaS from 1 microM to 100 microM were added in the presence and absence of a functional endothelium or in the presence and absence of an NO synthase inhibitor and a selective P2y antagonist. Acetylcholine (Ach)-induced relaxation was used in each experiment for control. RESULTS:In human precontracted corporal cavernosal strips with a functional endothelium (relaxed by acetylcholine) ADPbetaS induces a dose-dependent relaxation with maximal relaxation of 45.5+/-5.0% and an EC50 of 11.7 microM. The relaxant effect of ADPbetaS was reduced by 77.1+/-7.0% by reactive blue 2 (20 microM)(a P2y antagonist). L-NAME (L-Nitro Arginin Methyl Ester), an NO synthase inhibitor (100 microM), reduced Ach- and ADPbetaS- induced relaxations by 86.59+/-3.24% and 86.83+/-0.5% respectively. Ach- and ADPbetaS- induced relaxations were significantly inhibited after dislodging of the endothelial lining of the corporal cavernosal strips, 90.11+/-6.2% and 87.1+/-5% respectively. CONCLUSIONS:Human corporal cavernosal strips can be relaxed by stimulation of P2y purinoceptors via NO release. This relaxation is an endothelium-dependent mechanism. Purines may be implicated in physiological erection in man.

We conducted-two parallel studies on cryopreserved arterial homografts: a biomechanical study based on traction tests and a functional study coupled with a histology examination. Twenty-four arterial segments from 6 donors (2 iliac and 2 superficial femoral segments per donor) were cryopreserved at -150 degrees C and -80 degrees C. Cryopreservation lasted at least 6 months. Lengthening at rupture, the. Young elasticity module, and rupture stress were calculated from the traction test. Results were significantly different depending on the preservation temperature. The functional properties of the cryopreserved arterial grafts were evaluated by studying the vasomotricity capacity of the vascular smooth muscle (VSM) and the endothelium. The expected results (direct contracture of VSM induced by PHE and endothelial dependent relaxation of VSM induced by AGH) were measured on fresh arteries. Cryopreserved arteries showed no response to physiological doses of PHE and AGH, whatever the preservation temperature. In one-third off he cases, a lower amplitude vasoconstriction was obtained using nonphysiological doses of PHE; there was no relaxation with ACH.

This study investigates the effects of agents which act on the production or efficacy of free radicals on the hypoxic responses of rat aorta rings. Under moderate hypoxic conditions, the resting tension of the rings was not changed but in rings precontracted with 5-hydroxytryptamine, there was a relaxation followed by a contraction. Removal of the endothelium with saponin suppressed relaxation to acetylcholine and abolished the contractions produced by hypoxia. In rings with a functional endothelium, hypoxic vasoconstriction was strongly inhibited by mannitol and exifone, but was not reduced by NG-nitro-l-arginine methyl ester, superoxide dismutase+catalase, or deferoxamine. Hypoxic vasodilatation was only partially inhibited by mannitol. To conclude, hypoxic constriction of the rat thoracic aorta is largely endothelium-dependent and involves free radicals whereas hypoxic dilatation is partially endothelium-dependent and partially involves free radicals. There is also indirect evidence for lack of direct involvement of nitric oxide/endothelium-derived relaxing factor (NO°/EDRF), hydroxyl radical (OH°) and superoxide anion in the hypoxic constriction and relaxation of the rat aorta.

OBJECTIVE:The efficiency of contrast agents in medical imaging depends on their distribution into vascular and interstitial compartments. The aim of this study was to compare in vitro endothelial permeability to different classes of contrast agents with various vascular persistence properties: a triiodinated nonionic monomer (ioversol), an iodinated dextran polymer (P604), and an iron oxide nanoparticle (sinerem).METHODS:Permeability studies, through collagen-coated filters with or without porcine aortic endothelial cell monolayer, were carried out by placing each filter-ring (luminal chamber) into a beaker containing a culture medium (abluminal chamber). Contrast media, diluted in the culture medium, were added to the luminal chamber. Aliquots were sampled from the abluminal chamber for contrast agent determinations. The volume cleared of the compound was calculated from the luminal side to the abluminal side. Parallel permeability tests to [3H]-H2O and Evans blue albumin were performed as references. Finally, the modulatory effect of bradykinin on endothelial permeability to albumin or to contrast agents was studied.RESULTS:The volume cleared of ioversol, P604, and sinerem through membrane filters was decreased by 19.6%, 32.1%, and 52.0%, respectively, in the presence of a cell monolayer. Bradykinin (10(-6) M) significantly increased permeability to albumin, ioversol, and sinerem. Ioversol and sinerem induced a significant decrease in permeability to albumin.CONCLUSIONS:A relation between the molecular size of the contrast agents tested and their endothelial permeability can be established with this in vitro model.