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

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Abstract
The effects of prostacycline (PGI2) were compared with those of prostaglandin E1 (PGE1) on the cardiac hemodynamics (coronary blood flow, systemic blood pressure, cardiac output and maximum dp/dt [change of pressure with time] of the left ventricle) in closed-chest dogs. The effects of PGI2 were compared with those of PGE1 on the concentrations of the coronary arterial and myocardial cAMP and cGMP in open-chest dogs. The intraventricular and i.v. injection of 0.1-4.0 .mu.g/kg of PGI2 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 was 4 times as potent as PGE1. The effect of PGI2 on the systemic blood pressure was twice as potent as PGE1. The concentration of the coronary arterial cAMP was significantly increased by the administration of PGI2 and PGE1 (control group: PGI2 group was 0.201 .+-. 0.022 vs. 0.264 .+-. 0.017 pmol/mg tissue, P < 0.05; control: PGE1 was 0.201 .+-. 0.022 vs. 0.286 .+-. 0.027 pmol/mg tissue, P < 0.05). The concentrations of the coronary arterial cGMP were not significantly changed by the administration of PGI2 and PGE1, nor were those of myocardial cAMP and cGMP. 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.