AJP - Endocrinology and Metabolism, Vol 255, Issue 3 E229-E235, Copyright © 1988 by American Physiological Society
Responsiveness of isolated adrenocortical cells from lean and obese Zucker rats to ACTH
B. D. White, W. D. Davenport and J. R. Porter
Department of Physiology, Louisiana State University Medical Center, New Orleans 70112.
Morning plasma corticosterone concentrations have been reported to be
elevated in obese Zucker rats compared with lean rats. The aim of this
study was to determine if differences in adrenal sensitivity or maximal
responsiveness to adrenocorticotropic hormone (ACTH)-(1-24) could account
for this disparity. Serum and adrenal glands were collected from lean and
obese, male and female Zucker rats (10-13 wk old) between 10:00 and 11:00
A.M. Adrenocortical cells were isolated and challenged with ACTH-(1-24).
The serum corticosterone and ACTH concentrations were significantly greater
in obese males compared with lean males (45.3 +/- 10.3 vs. 23.2 +/- 1.45
ng/ml and 156.6 +/- 15.3 vs. 113.3 +/- 9.4 pg/ml, respectively). Although
serum corticosterone concentrations were similar in female rats, serum ACTH
concentrations tended (P = 0.07) to be lower in obese female rats than in
lean female rats (67.6 +/- 9.3 vs. 103.5 +/- 15.1 pg/ml, respectively). The
median effective concentration (EC50) and the maximal corticosterone
response per microgram of DNA of dose-response curves derived from lean and
obese rats were not significantly different. Additionally, a morphometric
evaluation of adrenal tissue from lean and obese rats suggested that cells
of the zona glomerulosa were smaller in obese rats than in lean rats. Our
data confirm that morning serum corticosterone concentrations are elevated
in 10- to 13-wk-old male Zucker rats. This difference does not appear to be
due to differences in the sensitivity or maximal secreting capacity of
adrenocortical cells to ACTH.
