Prostaglandin E<sub>2</sub> and Epinephrine Participate in Cyclical Reduction of Coronary Blood Pressure and Flow

Abstract

The effects of the agents that inhibited synthesis of prostaglandins (PGs) and thromboxanes (TXs) on cyclical reduction of blood flow in partially constricted coronary artery of anesthetized dog were examined. The cyclical reduction of coronary blood flow was eliminated by intravenous injections of aspirin that inhibited synthesis of endoperoxides, of benzydamine that inhibited synthesis of endoperoxides and TX A2, and of phenylbutazone that inhibited synthesis of PG E2, but was not of reduced glutathione that inhibited synthesis of TX A2 and accelerated synthesis of PG E2. In the preparations in which cyclical reduction of blood flow did not occur spontaneously, intracoronary injection of PG E2, but not of PG F2a, induced the cyclical reduction. The cyclical reduction was also induced by intravenous injections of epinephrine and reduced glutathione that accelerated synthesis of PG E2. The results indicate participation of PG E2 in the cyclical reduction of coronary blood flow.