PHARMACOLOGICAL ANALYSIS OF RESPONSES TO ATP IN THE ISOLATED AND PERFUSED CANINE CORONARY-ARTERY

Vascular responses of the isolated and perfused canine coronary artery to adenosine 5'-triphosphate (ATP) were analyzed pharmacologically. A t basal perfusion pressure, ATP induced a vasoconstriction followed by a vasodilation dose-dependently. The potency order for vasoconstricti on was alpha,beta-methylene ATP > 2-methylthio ATP > UTP > ATP. That f or vasodilation was ATP > 2-methylthio ATP > alpha,beta-methylene ATP >> UTP in the preparations precontracted by 20 mM KCl. Aminophylline i nhibited the vasodilation induced by adenosine, but not that induced b y ATP. alpha,beta-Methylene ATP and suramin inhibited the vasoconstric tion induced by ATP. Reactive blue 2 inhibited the vasodilation induce d by ATP, but not the vasoconstriction. Removal of the endothelium by saponin and L-N-G-nitroarginine inhibited the vasodilation induced by ATP, but indomethacin did not. The results suggest that ATP induces va soconstriction via P-2X purinoceptors on the smooth muscle and vasodil ation via P-2Y purinoceptors on the endothelium through mainly the rel ease of nitric oxide in the canine coronary artery, respectively. (C) 1997 Elsevier Science B.V.