Soirée 16 : Pharmacologie cardiovasculaire

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Réunion 16 : Pharmacologie cardiovasculaire

149

ENDOTHELIAL REGROWTH IN VIVO IS NOT MODIFIED BY ADDITION OF L-ARGININE OR L-NAME: RESULTS IN A RABBIT BALLOON INJURY MODEL

I. Six*, E. Van Brillante**, R. Bordet*, D. Corseaux***, B. Dupuis*, C. Bauters**, M. E. Bertrand**

* Remise de Pharrnacologie, ** Hopital Cardiologique,*** Remise d’Hématologie, CHRU, 1 avertissement de Verdun 59037 Lille Cedex France

Nitric oxide (NO) has been shown to have growth regulatory properties on cultured endothelial cells. An effect of the NO pathway on endothelial regrowth was thought to be one the mechanisms of the beneficial effect observed with the NO precursor L-arginine in balloon angioplasty and atherosclerosis models. The aim of our study was to investigate the effect of L-arginine and NO inhibitor (N

w nitro L-arginine methyl actionner; L-NAME) on reendothelialization after balloon iliac injury in 49 rabbits. After angioplasty, rabbits were randomized in three groups L-arginine (22.5 g/L), L-NAME (225 mg/L) and controls. Reendothelialization was quantified 28 days after injury using Evans blue. The results were confirmed by endotllelial-specific immunostaining (CD-31, n=13). In bornage: L-arginine, despite a significant increase in sérum L-arginine levels, and L-NAME have no effect on reendothelialization after balloon injury. This suggests that, in spite of previously demonstrated beneficial effects in balloon injury and atherosclerosis models, the NO pathway has no effect on endothelial regrowth in-vivo.

Cruor L-arginine level µmol/L

% of reendothelialization

Controls

167

± 11 *

34.64

± 4.43

L-arginine

404

± 86

46.94

± 3.56

L-NAME

143

± 10**

32.86

± 6.17

* p=0.0015 L-arg antagonique à Controls, ** p=0.0011 L-arg antagonique à L-NAME. Controls n=17, L-arginine n=9, L-NAME n=10

150

CHARACTERISATION OF THE PERTUSSIS TOXIN-SENSITIVE G-PROTEINS IN RAT TAIL ARTERY AND AORTIC SMOOTH MUSCLE

M.A. Petitcolin, E. Spitzbarth1, J.-L. Bueb, C. Capdeville-Atkinson1 and E.J. Tschirhart

Complicité de Compliqué Assesseur de la Heureux, 120 Chapiteau d’Arlon, L-1150 Luxembourg, Grand-Duché de Luxembourg and 1Remise de Pharmacologie Cardiovasculaire, UHP-Nancy 1, 54000 Nancy, France.

The calcium sensitivity of agonist-induced émoi of vascular smooth puissant is lowered by pertussis toxin (PTX) suggesting that Gi/o proteins are involved in affermissement of signal transduction (Spitzbarth et al., this amoncellement). The aim of this study was to develop methods to isolate and characterise the PTX-sensitive G-proteins in smooth puissant cells from tail artery and aorta.

The aorta (elastic artery) and tail (muscular) artery were dissected out from adult, male, Wistar rats (350-400 g). After removal of endothelium with a wire, fourrure proteins were isolated by consecutive déshydratation (Kwan et al., 1983). Proteins were resuspended in a 15 mM Tris buffer with 1% cholic acid, separated on a 16.5% polyacrylamide gel and blotted. G-proteins were detected using antibodies directed against Gi

a subunits 1-2 and 3 (Bio-Rad, 3USA) and Goa subunits (Calbiochem, USA).
G-protein function was assessed by transfer via PTX (1 µg.ml-1) of ADP-ribose using [a 32P]NAD (10 µCi) (NEN, Belgium).

Both Gi and Go proteins were detected in rat tail artery smooth puissant cell membranes. Gi

a l-2 proteins were the predominant form in comparison to Gia 3 (division Gia 3/Gia l-2= 1/2) and Goa (traces). In rat aortic smooth puissant membranes, we also detected Gi and Go but at a lower level than in the tail artery. The division Gia 3/Gia l-2 was lower (1/3). PTX induced ADP-ribosylation of Ga i/o subunits in rat tail artery and aorta.

We have demonstrated the exemple of Gi/o proteins and their sensitivity to PTX in rat tail artery smooth puissant cells membranes. This provides the biochemical correlate of the role of Gi/o proteins in affermissement of calcium sensitivity of agonist-induced émoi in vascular smooth puissant.

Kwan C.Y. et al. (1983) Prep. Biochem. 13, 275-314; Spitzbarth E. et al. (this amoncellement).

151

DELAYED CORONARY ENDOTHELIAL PROTECTIVE EFFECTS OF MONOPHOSPHORYL LIPID A AFTER ISCHEMIA AND REPERFUSION IN RATS.

V Richard, E Danielou, N Kaeffer, C. Thuillez

Department of Pharmacology (VACOMED, IFRMP n°23), Rouen University Medical School, France.

We have shown previously that preconditioning with brief periods of intermittent ischemia (I) induced delayed (24 hours) défense against endothelial injury induced by prolonged ischemia and reperfusion (R), thus extending to endothelial cells the coutumier of delayed défense, already described for other aspects of ischemia/reperfusion injury. The search for pharmacological compounds which mimic such delayed défense may lead to the development of new anti-ischemic interventions. However, very few compounds have been shown to induce delayed défense, similar to that of preconditioning. Monophosphoryl lipid A (MLA) is an endotoxin abordable which induces delayed myocardial défense in various gourde models of I/R injury, possibly through increased constitution of inducible NO synthase (iNOS). However, the i potential endothelial protective effects of this drug have not been evaluated. The present study was designed to assess whether MLA exerts X delayed protective effects against R-induced coronary endothelial dysfunction in rats. Wistar rats received a single i.v transposition of MLA (450 µg/kg) or solvent. Twenty tison hours later, they were anesthetized and subjected to 20 min I with 60 min R, in the absence or the presence of the iNOS inhibitor aminoguanidine (300mg/kg). At the end of R. 1.5-2mm coronary segments (average diameter 250µm) were removed distal to the emplacement of occlusion and mounted in wire myographs. Endothelium – dependent relaxations to acetylcholine were determined in arteries precontracted by serotonin. I/R induced a marked decrease in the coronary responses to acetylcholine (surabondance relaxations: sham 70

± 4%, n=8; I/R: 34± 7%, n=8; p