Circulatory effects of prostaglandin endoperoxide analogues studied in the dog during left ventricular bypass.

1. Intravenous administration of both the 9alpha,11alpha-(epoxymethano) and 11alpha,9alpha-(epoxymethano) analogues of prostaglandin H2 (0.25 microgram/kg) produced a prominent rise in pulmonary arterial pressure and a moderate increase in systemic arterial pressure. 2. Direct administration of the endoperoxide analogues (1.25 microgram/kg) into the bypass reservoir produced a greater rise in systemic arterial pressure and less prominent rise in pulmonary arterial pressure. 3. An intravenous dose of prostaglandin F2alpha that was 20 times larger was needed to produce a comparable rise in pulmonary arterial pressure. 4. The pulmonary and systemic pressor responses produced by the endoperoxide analogues were due to a direct increase in the vascular resistance.