AJP - Endocrinology and Metabolism, Vol 250, Issue 6 629-E633, Copyright © 1986 by American Physiological Society
Stimulation of corticosterone secretion in vitro by brief ACTH exposure
L. D. Keith, B. Tam and M. A. Greer
We examined the relationship between ACTH concentration and exposure
duration on stimulation of corticosterone (B) secretion in vitro using
perifused enzymatically dispersed rat adrenocortical cells. A modular
perifusion apparatus was used that permitted evaluation of 20-24 cell
chambers per experimental session. In expt 1, 20-1000 pg/ml concentrations
of synthetic ACTH-(1-24) were presented to cells for 1 min. In expt 2, 100
pg ACTH-(1-24) was presented to adrenal cells in five dose-duration
regimens ranging from 5 pg/min for 20 min to 100 pg/min for 1 min.
Perifusal rate was 1 ml/min in all sessions. B was determined by
radioimmunoassay. In expt 1 (constant-duration paradigm), 1-min
presentation of ACTH-(1-24) produced log-linear dose-response effects
across these concentrations (r = 0.926, P less than 0.01). In expt 2
(constant-mass paradigm), identical masses administered in different
dose-duration regimens had different steroidogenic efficacies (P less than
0.02): low-dose long-duration regimens provoked greater total release than
high-dose short-duration regimens. Overall, every dose-duration regimen was
associated with stimulation of B secretion. These results indicate that
very brief exposure to physiological concentrations of ACTH-(1-24) is a
significant stimulus for corticosteroid secretion; variations in the
dose-duration regimen over the physiological range modifies both the
maximum rate of secretion and the duration of secretion, but not the
response latency; and ACTH-(1-24) presentation mass is not the sole
determinant of B secretion.
