Cardiopulmonary actions of prostaglandin 6-keto-E1 in the anesthetized dog

The cardiopulmonary actions of prostaglandin (PG) 6-keto-E1, a newly discovered metabolite of PGI2, were investigated in the intact chest dog. Injections of 6-keto-PGE1 into the superior vena cava in doses of 1-30 microgram caused dose-dependent decreases in pulmonary arterial and systemic arterial pressures. Inasmuch as cardiac output increased and left or right atrial pressure was unchanged, the decreases in pulmonary and systemic vascular resistances. Reductions in systemic arterial pressure and systemic vascular resistance were similar when 6-keto-PGE1 was injected into the superior vena cava or into the left atrium suggesting that this newly discovered substance is not inactivated in transit through the pulmonary vascular bed in the dog. Decreases in pulmonary arterial pressure and pulmonary vascular resistance were enhanced when pulmonary vascular tone was elevated by infusion of a stable prostaglandin endoperoxide analog or 15-methyl-PGF2 alpha. The present results demonstrate that 6-keto-PGE1 has significant vasodilator activity in pulmonary and systemic vascular beds in the dog and since this substance is not inactivated in the lung, it would serve as a circulating hormone in this species.