EVIDENCE AGAINST THE ADENOSINE-CATECHOL AMINE ANTAGONISM IN THE IN SITU DOG HEART: 183

Abstract

Adenosine has been reported to attenuate the positive inotropic effects of catecholamines in in vitro-heart preparations of rodents. These results were not confirmed in anesthetized dogs during intracoronary infusion of isoproterenol. However, these experiments did not study the effects of adenosine on the inotropic effects of endogenously released catecholamines. Therefore we performed cardiac sympathetic nerve stimulation (CSNS) in 5 anesthetized, vagotomized dogs. The left circumflex coronary artery was perfused at a constant pressure of 130±4 mmHg. The contractile function of the circumflex-perfused myocardium was analyzed by sonomicrometry. CSNS at 1, 2, 5, 10 and 20 Hz increased systolic segment shortening (SS_cx) in a frequency-dependent manner from 10.9±2.6 at control to 15.3±3.4 % at 20 Hz. During intracoronary infusion of adenosine (50 μg/ kg/min) CSNS still increased SS_CX frequency-dependently from 9.9±3.5 to 16.3±4.5 %. The lack of any adenosine-catecholamine antagonism in our experiments was not due to the sequence of procedures, nor to the marked flow increase induced by adenosine, since SS_CX at rest was rather reduced with adenosine infusion and since during intracoronary infusion of papaverine and sodium-nitroprusside similar results were obtained. It seems that the observation of adenosine-catecholamine antagonism in rodents is a species dependent phenomenon. Supported by SFB 30 - Kardiologie, Düsseldorf

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