Steroid production and membrane potential measurement in cells of the adrenal cortex

Abstract

The relation between corticosteroid production and the cellular membrane potential of adrenocortical cells has been investigated using a flow system for the incubation in vitro of adrenal glands from neonatal rabbits. Corticosteroid production by the adrenal cells was determined by a fluorescence method; membrane potentials were measured with glass micro-electrodes. Adrenocorticotrophic hormone (ACTH) increased corticosteroid production without altering the membrane potential of the adrenocortical cells. Conversely, a 5-fold increase in [K]o did not increase corticosteroid production but decreased the cellular membrane potential. The increase in [K]o did not impair the stimulation of cortlcosteroid production by ACTH. The log dose-response relation between the concentration of ACTH in the incubation medium and the amount of corticosteroid produced by the adrenal tissue was linear. No evidence was found of a direct relation between the pro-duction of corticosteroid by adrenocortical cells and the cellular mem-brane potential. Indeed, the output of steroid appeared to be relatively independent of the polarization of the cell membrane.