8-iso PGE2 is one of several isoprostanes produced from arachidonic acid during lipid peroxidation. It is a potent renal vasoconstrictor in the rat. 8-iso PGE2 inhibits U-46619 or I-BOP-induced platelet aggregation with IC50 values of 0.5 and 5 µM, respectively. When infused into the renal artery of the rat at a concentration of 4 mg/kg/min, 8-iso PGE2 decreases the GFR and renal plasma flow by 80% without affecting blood pressure.