Two types of cytochrome P-450(11 beta) in rat adrenals: separate regulation of gene expression.

Northern blot hybridization with specific oligonucleotide probes was used for assaying steady state concentrations of the mRNAs encoding the two types of rat cytochrome P-450(11 beta), i.e. CYP11B1 (non-aldosterone-producing) and CYP11B2 (aldosterone-producing). The zona glomerulosa level of CYP11B2 mRNA was raised by potassium repletion or sodium restriction and was lowered by potassium depletion or by the administration of deoxycorticosterone, ACTH or dexamethasone. In all zones of the adrenal cortex, the CYP11B1 mRNA level was decreased upon dexamethasone treatment. Only in the zona glomerulosa it was increased upon mineralocorticoid treatment and decreased upon potassium repletion or sodium restriction. According to this evidence, the expression of the two genes encoding the two isozymes (CYP11B1 and CYP11B2) in rat zona glomerulosa cells is separately regulated. Whereas CYP11B2 expression is controlled mainly by angiotensin II and extracellular potassium, ACTH is the major but not the only factor controlling CYP11B1 expression in these cells.