The effects of corticosterone and cortisol in concentrations attainable in the adrenal gland were studied on ACTH-induced steroidogenesis in cultured cortical cells of foetal human and rat adrenals. Corticosterone at a concentration of 5.8 × 10−5 mol/l clearly inhibited cortisol production (65.5%; P < 0.005) and simultaneously increased androgen production in tissue culture of foetal human adrenals. Cortisol at a concentration of 2.8 × 10−4 mol/l clearly inhibited 18-OH-DOC (74.0 %, P < 0.001) and aldosterone (83.7 % P < 0.005) production in tissue culture of foetal rat adrenals. In primary culture of foetal human adrenals cortisol did not decrease aldosterone production absolutely, but it significantly decreased the relative amount of aldosterone with respect to corticosterone. Cortisol did not inhibit corticosterone production in either culture.
The results demonstrate that cortisol and corticosterone have qualitatively different effects on adrenal steroidogenesis and that these steroids may play a basic role in the functional zonation of the adrenal gland.