Effects of gestation on enzymes controlling aldosterone synthesis in the rat adrenal

In the present study, the effects of gestation on various enzymes implicated in corticosteroid synthesis were evaluated in adrenal zona glomerulosa and zona fasciculata-reticularis of the Sprague-Dawley rat. The activity and expression of cholesterol side-chain cleavage cytochrome P450, 11 beta-hydroxylase cytochrome P450, and aldosterone synthase cytochrome P450 (P450aldo) were analyzed. Plasma aldosterone levels were increased significantly at 22 days gestation (n = 10) and fell below the nonpregnant levels at 18-36 h postpartum (n = 11). The activity and expression of 11 beta-hydroxylase cytochrome P450 and cholesterol side-chain cleavage cytochrome P450 were not modified by gestation. P450aldo activity increased at 14 days gestation (n = 4) and returned to the prepregnancy level at 2 weeks postpartum (n = 5). As shown by Northern blot analysis (n = 3), P450aldo messenger RNA increased significantly at 22 days gestation and decreased 18-36 h postpartum. We clearly demonstrated that elevated plasma aldosterone levels during pregnancy are associated with augmented activity and messenger RNA levels of P450aldo in the zona glomerulosa.