Hypotensive and other cardiovascular effects of arachidonic acid in rabbits.

Intravenous administration of arachidonic acid lowers systemic arterial pressure in conscious and anesthetized rabbits. This hypotensive response does not show tachyphylaxis and is blocked by aspirin. The hypotension on i.v. administration is due to both a decrease in cardiac output and a decrease in systemic vascular resistance. The decrease in cardiac output is accompanied by a severe pulmonary hypertension and right ventricular failure. Upon i.a. arachidonic acid administration, the hypotension is due to a decrease in systemic vascular resistance. It is proposed that arachidonic acid is transformed predominantly into a vasoconstrictor metabolite in the pulmonary vascular bed and vasodilator metabolite in the systemic vascular bed. The nature of the metabolite remains to be established.