REGULATION OF ADRENAL STEROIDOGENESIS BY ADRENALINE - EXPRESSION OF CYTOCHROME P450 GENES

The effect of adrenaline on the secretion of cortisol and cyclic AMP (cAMP) and on the accumulation of four different mRNAs encoding cholesterol side-chain cleavage cytochrome P450 (P450scc), 17alpha-hydroxylase cytochrome P450 (P450(17alpha)), 21-hydroxylase cytochrome P450 (P450c21) and 11beta-hydroxylase cytochrome P450 (P450(11beta)) was studied iri bovine adrenocortical cells in primary culture and compared with the effects of ACTH. Treatment of cultured cells with adrenaline (1-100 mumol/l) showed a biphasic response in cortisol release over 1-24 h. Concentration of cAMP in the culture media increased from a basal level of <0.06 pmol/dish to a maximal level of 40.14+/-8.9 pmol/dish with a half-maximal release of 20.07 pmol cAMP/dish in the medium reached 1.2 h after treatment with 10 mumol adrenaline/l. This stimulation resulted in an uniform increase in the levels of all four P450 mRNAs as revealed by Northern blot analysis. Increasing doses of adrenaline produced a maximal mRNA accumulation at a concentration of 10 mumol adrenaline/l. Incubation of the cells with 10 mumol adrenaline/l for 1-24 h produced a biphasic time-Course with a half-maximal stimulation after about 5-6 h. Maximal stimulation with ACTH (100 nmol/l) caused different accumulations of the four mRNAs: P450sec mRNA increased twice as much and P450(17alpha) mRNA six times as much as the accumulation of P450c21 mRNA and P450(11beta) mRNA, which was about ten-fold over basal values. Propranolol totally blocked the stimulatory effect of adrenaline but not the effect of ACTH. Our data suggest that the stimulatory effect of adrenaline upon de-novo cortisol formation is regulated in part at the transcriptional level in a dose- and time-dependent manner. The regulation requires beta-adrenergic receptors and is due to a cAMP-mediated increase in the accumulation of all four P450 mRNAs.