Administration of losartan (L), an angiotensin II receptor antagonist, at a daily dose of 3 mg/kg body wt, lowered systolic blood pressure (SBP) in both the Prague hypertensive rat and the Prague normotensive rat (PNR). Proteinuria was markedly reduced in both strains by L. Seven days after kidney ischemia due to bilateral clamping of both renal arteries for 45 minutes, the renal function (endogenous creatinine clearance, sodium, potassium, and urea excretion rates) was completely normal in L-treated PHR and PNR, whereas distinct deterioration was observed in untreated animals. The survival rate after kidney ischemia was significantly improved by L in both PHR and PNR. Thus, L had a significant blood pressure-lowering action in both strains and exerted a distinct renal protective effect from kidney ischemia.