Inhibition of corticosteroid production by sodium pentobarbitone in rat adrenocortical preparations.

It is possible that some of the effects of sodium pentobarbitone on the hypothalamo-pituitary-adrenal axis in the intact animal may be attributable to direct actions on the adrenal cortex. The effects of the barbiturate on steroid production by rat adrenal preparations in vitro have therefore been examined. In zona glomerulosa cells, pentobarbitone inhibited basal steroid production in a dose-related fashion. For aldosterone and corticosterone, the doses required for 50% inhibition of production (IC50) were 1.2 mmol pentobarbitone/l and 3.7 mmol/l respectively. Steroidogenesis was inhibited at lower levels of pentobarbitone in the presence of 1 nmol ACTH/l (IC50 = 0.5 mmol pentobarbitone/l for aldosterone and 2.2 mmol/l for corticosterone). In zona fasciculata/reticularis cells, production of corticosterone was similarly reduced with an IC50 of 2.8 mmol pentobarbitone/l for basal production and 1.3 mmol/l for ACTH-stimulated production. The dose-related increases in corticosterone production produced by ACTH (0.1-1000 pmol/l) or dibutyryl cyclic AMP (0.1-1.0 mmol/l) were also eliminated in the presence of 2 mmol pentobarbitone/l. The effects of pentobarbitone (1-4 mmol/l) on the production of pregnenolone and deoxycorticosterone (DOC) were also studied. In zona fasciculata/reticularis cells, the responses of both pregnenolone and DOC were bell-shaped with increases at 1 mmol pentobarbitone/l, which fell back to control levels at 4 mmol pentobarbitone/l. Stimulation of DOC, accompanied by decreases in aldosterone and corticosterone production, was also seen in zona glomerulosa cells at 1 mmol pentobarbitone/l.(ABSTRACT TRUNCATED AT 250 WORDS)