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

1. 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.2. Adrenocorticotrophic hormone (ACTH) increased corticosteroid production without altering the membrane potential of the adrenocortical cells. Conversely, a 5-fold increase in K did not increase corticosteroid production but decreased the cellular membrane potential. The increase in K did not impair the stimulation of corticosteroid production by ACTH.3. 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.4. No evidence was found of a direct relation between the production of corticosteroid by adrenocortical cells and the cellular membrane potential. Indeed, the output of steroid appeared to be relatively independent of the polarization of the cell membrane.