Ischemia and subsequent reperfusion are known to impair renal function. We examined several agents that might prevent renal impairment or enhance the recovery of renal function after ischemia/reperfusion injury in rats. Different degrees of preventive effects were observed in rats treated with captopril, BQ-123 (endothelin type A receptor antagonist), sodium nitroprusside (SNP, a nitric oxide donor), and losartan (angiotensin II type 1 receptor antagonist). Only minimal changes in renal morphology were observed after treatment with losartan, SNP, captopril, and BQ-123 compared with control animals. On the other hand, lesions were prominent in the N(G)-nitro-L-arginine-methyl ester (L-NAME)- and L-arginine-treated rats. The Na(+)-K(+) ATPase activity of ischemic kidneys was, however, preserved in all treatment groups, except in those treated with L-arginine and L-NAME, which showed a marked reduction in Na(+)-K(+) ATPase activity. Our post-treatment data suggest that losartan and SNP have the greatest potential for therapeutic use to mitigate post-ischemic renal damage and functional impairment.