AJP - Endocrinology and Metabolism, Vol 255, Issue 6 E903-E911, Copyright © 1988 by American Physiological Society
Structure and function changes in rat adrenal glands during aging
E. Reaven, M. Kostrna, J. Ramachandran and S. Azhar
Geriatric Research, Education, and Clinical Center, Veterans Administration Medical Center, Palo Alto 94305.
The current study examines corticosterone production in young and old rats
with a view to understanding how hormone production is related to aging
changes in the adrenal gland. For this purpose, we compared total (plasma
volume-corrected) values for adrenocorticotropic hormone (ACTH)-induced
maximal corticosterone production in young, mature (5-mo-old), and aging
(18-mo-old) rats. These values were subsequently corrected for measured
age-related differences in adrenal weight, adrenal cortex volume, specific
adrenal zone volumes, and total number of corticosterone-producing cells in
the adrenals of the differently aged rats. In addition, corticosterone
disposal rates were measured in the two groups of rats, and adrenal
cortical ACTH binding sites were identified by autoradiography after
perfusion with 125I-labeled ACTH analogue. The results show that maximal
serum ACTH-induced corticosterone concentrations (per ml serum) in the
18-mo-old rats are somewhat less than those seen in the younger animals.
However, because the plasma volume is greater in the older animals (and
corticosterone disposal rates do not vary), total circulating
corticosterone production is, in fact, equivalent in the two groups of
animals. When these total values for corticosterone are corrected for
various structural changes in the adrenal gland with age, corticosterone
production was found to be lower in the older group of rats: i.e., one sees
an approximately 50% decline when corticosterone is expressed per adrenal
weight or zonal volume and an approximately 20% decline when expressed per
number of endocrine cells per adrenal.(ABSTRACT TRUNCATED AT 250 WORDS)
