Regulation of AT(1) receptor mRNA expression is an important determinant of angiotensin II-induced steroidogenesis. We have PCR-amplified the bovine adrenal AT(1) receptor coding region using primers designed from the published bovine AT(1) receptor sequence. This has been used as a probe on Northern blots to detect changes in the levels of AT(1) receptor mRNA in primary cultures of bovine zona fasciculata cells in response to activation of several different signal transduction mechanisms in additon to two major adrenal steroid products, cortisol and aldosterone. AT(1) receptor mRNA decreased in response to 6hr AII (10 nM) treatment, but returned to basal levels following 48h AII treatment. This effect was mimicked by the phorbol ester PMA (1 mu M) and the calcium ionophore A23187 (1 mu M), both singly and in combination. Activation of the cAMP pathway by ACTH (1 nM) and 8-bromo-cAMP (0.1 CIM) also decreased AT(1) receptor mRNA levels. In contrast, both IGF-1 (10 ng/ml) and potassium ions (12 mM) increased the levels of AT(1) receptor mRNA. Finally, cortisol (10 mu M) but not aldosterone (100nM) decreased AT(1) receptor mRNA. We conclude that the regulation of AT(1) receptor mRNA in bovine zona fasciculata cells could involve several different signal transduction systems in addition to adrenocortical steroids themselves.
|Number of pages||6|
|Publication status||Published - 1996|