Estrogen Regulates Adrenal Angiotensin AT1Receptors by Modulating AT1Receptor Translation

Hypertension and associated cardiovascular disease increase after menopause. Angiotensin AT(1) receptor (AT(1)R) antagonists are effective treatments, in part, by inhibiting angiotensin II (Ang II)-induced aldosterone release from the adrenal zona glomerulosa (ZG). Estrogen decreases the number of AT(1)Rs in the adrenal gland and attenuates acute Ang II-induced aldosterone release. Here, we examined the effects of 17beta-estradiol (E(2)) on AT(1)R gene regulation in the rat adrenal cortex (AC). Female rats were ovariectomized and injected with vehicle or E(2). Immunohistochemistry revealed the presence of both estrogen receptor (ER)alpha and ERbeta in the ZG, and E(2) treatment increased the intensity of their nuclear staining. Under conditions in which AT(1)R maximal binding capacity was decreased by 46%, chronic miniosmotic pump Ang II-induced aldosterone secretion was reduced by 43%. E(2) treatment had no effect on AT(1a)R and AT(1b)R mRNA levels in the AC, whereas the AT(1)R mRNA polysome distribution in sucrose gradients was shifted to lighter fractions, indicating that E(2) treatment reduces AT(1)R translation. RNA binding proteins (RBPs) in AC extracts formed complexes with the 5' leader sequence (5'LS), coding region, and the 3'-untranslated region (3'UTR); however, only the activity of 5'LS RBPs was regulated by E(2) treatment. These data suggest that E(2), acting through its receptors in the ZG, reduces AT(1)R density and Ang II-induced aldosterone release, primarily by inhibiting AT(1)R translation, possibly by blocking ribosomal scanning caused by increased steric hindrance from 5'LS RBPs. Dysregulation of this posttranscriptional mechanism may contribute to the increased incidence of cardiovascular disease associated with menopause.