The effect of adrenaline on the accumulation of mRNA encoding cholesterol side-chain cleavage cytochrome P450 (P450scc) and cortisol secretion was studied in bovine adrenocortical cells in primary culture. Treatment of cultured cells with adrenaline resulted in a 2-fold increase in mRNA encoding P-450scc, as revealed by Northern blot analysis. Under these conditions the maximal stimulation with ACTH resulted in a 6-fold accumulation of mRNA encoding P450scc. The effect of adrenaline on the expression of P450scc was abolished by the beta-blocker propranolol, while propranolol had no effect on ACTH-induced P450scc mRNA accumulation. Adrenaline stimulated the secretion of cortisol in a dose-dependent manner with a median effective dose of 0.5 mumol/l. The adrenaline-stimulated cortisol secretion amounted to 42% of the effect of ACTH (0.1 nmol/l). Upon adrenaline treatment, cAMP concentration in the culture medium increased about 50-fold over the basal value. It is concluded that the stimulatory action of adrenaline upon cortisol formation requires beta-adrenergic receptors and is due, at least in part, to a cAMP-mediated increases in the accumulation of mRNA encoding P450scc.