Prostaglandin E2 and Epinephrine Participate in Cyclical Reduction of Coronary Blood Pressure and Flow

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Abstract
The effects of the agents that inhibited synthesis of prostaglandins (PG) and thromboxanes (TX) on cyclical reduction of blood flow in the partially constricted coronary artery of anesthetized dogs were examined. The cyclical reduction of coronary blood flow was eliminated by i.v. 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 eliminated by 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 F2.alpha., induced the cyclical reduction. The cyclical reduction was also induced by i.v. 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.