Sympathoadrenal regulation of adrenocortical steroidogenesis

Abstract

Sympathoadrenal regulation of adrenocortical steroidogenesis was studied on a physiological, cellular, molecular and morphological level. The effects of nerve activation and of epinephrine (EPI) on adrenal corticosteroid release were compared in isolated perfused pig adrenals with preserved nerve supply. Splanchnic nerve activation as well as perfusion with EPI provoked a siginificant release of cortisol, aldosterone and androstenedione. In cultured bovine adrenocortical cells steroid secretion and accumulation of P450_SCC, P450_17α, P450_c21 and P450_11β mRNAs were studied after stimulation with EPI with or without propranolol or phentolamine. Incubation with EPI stimulated steroidogenesis and increased the levels of all four P450-mRNAs. The β-adrenergic antagonist propranolol totally blocked the effects of EPI while the α-antagonist phentolamine had no effect. Using immunohistochemistry, adrenals were studied morphologically. The contact zones of the two cell types were investigated on an electron microscopical level. Cortical and medullary cells were closely interwoven with cortical and chromaffin cells in direct apposition, providing the possibility for paracrine interactions. It is concluded that the release of corticosteroids can be stimulated through the sympatho-adrenal system. The stimulatory action of EPI upon adrenal steroid formation and accumulation of all four P450-mRNAs requires C-adrenergic receptors. Taking into consideration the close colocalization of cortical and medullary tissue, this stimulation may be mediated by chromaffin cells in a paracrine manner.