EFFECTS OF GESTATION ON ENZYMES CONTROLLING ALDOSTERONE SYNTHESIS IN THE RAT ADRENAL

In the present study, the effects of gestation on various enzymes impl icated in corticosteroid synthesis were evaluated in adrenal zona glom erulosa and zona fasciculata-reticularis of the Sprague-Dawley rat. Th e activity and expression of cholesterol side-chain cleavage cytochrom e P450, 11 beta-hydroxylase cytochrome P450, and aldosterone synthase cytochrome P450 (P450aldo) were analyzed. Plasma aldosterone levels we re increased significantly at 22 days gestation (n = 10) and fell belo w 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. P4 50aldo activity increased at 14 days gestation (n = 4) and returned to the prepregnancy level at 2 weeks postpartum (n = 5). As shown by Nor thern blot analysis (n = 3), P450aldo messenger RNA increased signific antly at 22 days gestation and decreased 18-36 h postpartum. We clearl y demonstrated that elevated plasma aldosterone levels during pregnanc y are associated with augmented activity and messenger RNA levels of P 450aldo in the zona glomerulosa.