Cytochrome P450-dependent metabolites of arachidonic acid (AA) are increased in the kidneys of spontaneously hypertensive rats (SHR) as compared to control rats (WKY) in the period of rapid elevation of blood pressure (BP) from 5 to 13 weeks. We treated rats with stannous chloride (SnCl2) (10 mg/100 g body weight/day for 4 days) to decrease selectively renal cytochrome P450 content through increasing renal heme oxygenase activity. A decrease in renal cytochrome P450-dependent AA metabolites was associated with decreased BP and increased urinary Na+ excretion in 7- but not in 20-week-old SHR rats. Chronic treatment with SnCl2 (10 mg/100 g body weight twice a week) from 5 to 20 weeks prevented the elevation of BP in SHR rats. Further, the antihypertensive effects of tin persisted for 7 weeks beyond its discontinuation. BP in WKY rats was unaffected by tin. Both the acute and chronic treatment with tin are the first studies to demonstrate amelioration of hypertension in SHR by an intervention which is targeted at a single enzyme system.