Infusion of prostacyclin (PGI2) reportedly attenuates renal ischemic injury in the dog and the rat. In the dog, PGI2 is a potent renal vasodilator; in the rat a direct action on the renal vasculature is not always apparent. To determine whether or not the protective effect of PGI2 on postischemic ARF was hemodynamically mediated, studies were performed in uninephrectomized Sprague-Dawley rats before and after a 40 minute period of complete renal artery occlusion. In response to the preischemic infusion of PGI2 for 30 minutes at 160 ng/kg body wt/min i.v. (N = 7), MAP and RBF fell to 86 +/- 7% (P less than 0.0001) and 84 +/- 9% (P less than 0.05) of baseline values, respectively. RVR initially declined to 81 +/- 9% of baseline values (P less than 0.025) but returned to 102 +/- 13% of baseline values prior to the period of ischemia. Following the period of ischemia, reflow of blood in the rats receiving PGI2 was delayed when compared to rats not receiving PGI2 (N = 7). RBF returned to only 76 +/- 19% of the initial values in PGI2-treated rats (P less than 0.01) but to 90 +/- 12% of the initial values in rats receiving buffer alone (NS).(ABSTRACT TRUNCATED AT 250 WORDS)