AJP - Endocrinology and Metabolism, Vol 247, Issue 4 483-E488, Copyright © 1984 by American Physiological Society
Excess in vitro prolactin secretion by pituitary cells from ovariectomized old rats
M. Haji, G. S. Roth and M. R. Blackman
Various in vivo and in vitro pituitary lactotropic and gonadotropic
functions were measured in mature (6-7 mo, normally cycling) and old (24
mo, constant diestrus) female Wistar rats. Serum prolactin (PRL) levels
were higher (P less than 0.001), whereas luteinizing hormone (LH) values
were similar (P greater than 0.05) in old versus mature rats both before
and 3 days after ovariectomy. Serum PRL levels decreased significantly (P
less than 0.005) postovariectomy only in the mature rats. The in vitro
release of PRL and LH was measured for 4 days in primary adenohypophyseal
cell cultures from the ovariectomized rats. Both basal and 17
beta-estradiol (E2)-stimulated PRL release (P less than 0.001) and
production (P less than 0.005) were greater by cells from old rats. In
contrast, both basal release and E2-stimulated LH release were greater (P
less than 0.001) by cells from mature rats. Peak PRL release by cells from
both old and mature rats occurred after exposure to E2 doses 1/100th of
those required for peak LH release. These data support the hypothesis that
intrinsic derangements in anterior pituitary function contribute to the
reproductive decline in aging female rats and that different pituitary cell
types exhibit discordant age changes in estrogenic sensitivity.
