17β-estradiol alters isoproterenol-induced relaxation in rat aortic rings

Female Wistar rats were treated with 17 beta-estradiol (E-2) (10 mu g, s.c.) or with sesame oil for 3 days. The relaxation induced by isoproterenol (10(-9)-3 x 10(-6) M) in aortae precontracted with norepinephrine was significantly suppressed in aortae from E-2-treated rats compared with the relaxation in those from control rats. N-G-Nitro-L-arginine, a nitric oxide synthase inhibitor, inhibited isoproterenol-induced relaxation in aortae from both E-2-treated and control rats. Metyrapone, a cytochrome P450 monooxygenase inhibitor, inhibited it in aortae from control rats, but metyrapone enhanced the maximum relaxation in aortae from E-2-treated rats. These results suggest that E-2 modulates isoproterenol-induced vasodilation through nitric oxide and cytochrome P-450-dependent metabolites.