Actions of prostaglandin E2 on myocardial mechanics, coronary vascular resistance and oxygen consumption in the guinea-pig isolated heat preparation.

1 In isolated, electrically driven (3 Hz) hearts of guinea-pigs the action of prostaglandin E2 on left ventricular pressure (LVP), oxygen consumption (Qo2) and coronary vascular resistance (CVR) was studied by establishing cumulative concentration-response curves. The hearts were perfused at a constant flow (10 ml/min) with Tyrode solution (Ca++ 1.8 mM) at 32 degrees C. 2 Under control conditions prostaglandin E2 (2.86 X10(-11) -1.43 X 10(-7) M) decreased LVP, QO2 and CVR in a concentration-dependent manner by maximally 27, 18 and 38%, respectively (P less than 0.05). 3 After reserpine pretreatment there were lower initial values for all parameters measured. The effect of prostaglandin E2 on LVP and QO2 was abolished, but CVR was further diminished, depending on the concentration. 4 The results seem to support the hypothesis of an interaction of prostaglandin E2 with endogenous catecholamines as far as the effects on LVP and QO2 are concerned. In contrast, prostaglandin E2 seems to have a direct action on CVR, which is independent of the presence of catecholamines.