Journal of Neuroscience, Vol 5, 2161-2168, Copyright © 1985 by Society for Neuroscience
Glucocorticoid receptors and regulation of phenylethanolamine-N- methyltransferase activity in cultured chromaffin cells
KL Kelner and HB Pollard
Glucocorticoids are known to regulate the enzyme phenylethanolamine-N-
methyltransferase (PNMT) in the adrenal medulla of the rat and are thereby
thought to control the synthesis of epinephrine. We have examined the
details of this relationship in a simplified system, chromaffin cell
primary cultures derived from bovine adrenal medulla. Cultured chromaffin
cells were found to have a cytosolic, high affinity, saturable
glucocorticoid-binding protein with the steroid specificity of a classical
glucocorticoid receptor and a Kd of approximately 1 nM. Treatment of
cultured cells with dexamethasone or hydrocortisone at any time up to 21
days in culture increased PNMT activity in the soluble fraction of the
cell. The concentration of hormone required to produce a half-maximal
response was 10 nM dexamethasone when cells were cultured in the presence
of 5% fetal calf serum, or 1 nM in a defined serum-free medium. These
dose-response relationships are consistent with mediation of this effect by
the glucocorticoid receptor. Unexpectedly, however, the glucocorticoid-
induced increment in PNMT activity was not inhibited by cycloheximide at
concentrations up to 50 microM, and an acceleration of protein synthesis by
insulin treatment did not augment the glucocorticoid effect on PNMT.
Treatment of the cells with dexamethasone (100 microM) prevented the
decline in the epinephrine-to-norepinephrine ratio seen over time in
culture, an effect consistent with increased PNMT activity. However, there
was no effect of dexamethasone on the ability of the cells to secrete
catecholamines in response to stimulation with high KCl or 30 microM
nicotine.(ABSTRACT TRUNCATED AT 250 WORDS)