EFFECT OF ADENOSINE ON MYOCARDIAL OXYGEN BALANCE

Abstract

The present study was designed to determine the effect of adenosine on oxyhemoglobin equilibrium (P-50) and myocardial 02 consumption (M.ovrhdot.VO2) in the isolated supported dog heart preparation perfused at a constant coronary blood flow. Heart rate was controlled at 150 beats/min. A 3-min intracoronary infusion of adenosine (10, 50 and 100 .mu.g/min) produced significant decreases in M.ovrhdot.VO2, whereas coronary venous P-50 did not change. 5''-AMP infusion (70 and 140 .mu.g/min) did not significantly change M.ovrhdot.VO2. Both adenosine and 5''-AMP caused equivalent decreases in coronary artery perfusion pressure and peak left ventricular systolic pressure. Adenosine (50 and 100 .mu.g/min) produced a significant decrease in M.ovrhdot.VO2 of the isolated supported fibrillating heart. The reduction in M.ovrhdot.VO2 observed with adenosine may not be related to coronary vasodilation or to a negative inotropic or chronotropic action. Theophylline (2.5 mg/kg) partially blocked the hemodynamic effects of adenosine while completely abolishing the decrease in M.ovrhdot.VO2. Neither inosine nor hypoxanthine (50 and 100 .mu.g/min) changed M.ovrhdot.VO2, P-50 or myocardial hemodynamics. In addition to its proposed role in coronary blood flow regulation, adenosine appears to exert important effects on myocardial metabolism.