Prostaglandins and cyclic nucleotides: effects of PGI2 and PGE1 on cardiac hemodynamic and coronary arterial and myocardial cyclic nucleotide levels in dogs.

The effects of prostacyclin (PGI2) were compared with those of prostaglandin E1 (PGE1) on the cardiac hemodynamics (coronary blood flow, systemic blood pressure, cardiac output and max dp/dt of the left ventricle) in closed-chest dogs. Moreover, the effects of PGI2 were compared with those of PGE1 on the concentrations of the coronary arterial and myocardial cyclic adenosine 3':5'-monophosphate (cyclic AMP) and cyclic guanosin 3':5'-monophosphate (cyclic GMP) in open-chest dogs. The intraventricular and intravenous injection of 0.1 to 4.0 microgram/kg of POGI2 increased the coronary blood flow and decreased the mean systemic blood pressure. Comparison of dose response curves for PGI2 and PGE1 in relation to the coronary blood flow indicated that PGI2 and 4 times as potent as PGE1. On the other hand, the effect of PGI2 on the systemic blood pressure was twice as potent as PGE1. The concentration of the coronary arterial cyclic AMP was significantly increased by the administration of PGI2 and PGE1 (control group: PGI2 group was 0.201 +/- 0.022 vs. 0.264 +/- 0.017 pmoles/mg tissue, p < 0.05; control: PGE1 was 0.201 +/- 0.022 vs. 0.286 +/- 0.027 pmoles/mg tissue, p < 0.05). The concentrations of the coronary arterial cyclic GMP were not significantly changed by the administration of PGI2 and PGE1, nor were those of myocardial cyclic AMP and cyclic GMP. The changes in cyclic nucleotide levels and cardiac hemodynamics induced by PGI2 were qualitatively similar to those induced by PGE1, but the change caused by PGI2 was greater than PGE1 in the coronary and systemic hemodynamics.