AJP - Endocrinology and Metabolism, Vol 253, Issue 3 E233-E237, Copyright © 1987 by American Physiological Society
Ionophore A23187 partially reverses LH secretory defect of pituitary cells from old rats
R. S. Chuknyiska, M. R. Blackman and G. S. Roth
We measured in vitro release of luteinizing hormone (LH) in the presence of
1.5 mM extracellular calcium, with and without LH-releasing hormone (LHRH;
10(-10) to 10(-7) M) or the ionophore A23187 (10(-7) to 10(-4) M), in
primary cultures of anterior pituitary cells from intact mature (6 mo) and
old (24 mo) male and intact and ovariectomized mature and old female Wistar
rats. Base-line as well as LHRH- and A23187-mediated LH secretion was
decreased from cells of old rats. However, exposure to A23187 led to a
nearly twofold greater augmentation of LH release from cells of old rats,
thus decreasing the apparent age-related LH secretory deficit by
approximately one-half. We then measured LHRH-mediated (10(-8) M) vs.
A23187-mediated (10(-4) M) LH release with and without extracellular
calcium (0.08-1.5 mM). For cells from both mature and old rats, there was a
similar calcium dependency for A23187- and LHRH-mediated LH release, with
optimal LH secretion at 1.0-1.5 mM extracellular calcium concentrations.
Again, both LHRH- and A23187-stimulated LH release was significantly lower
and exposure to A23187 led to a greater increase in LH release from cells
of old rats. Taken together with similar findings in other systems, these
data suggest that the in vitro LH secretory defect of pituitary cells from
old rats results in part from one or more defects in calcium mobilization
and that such alterations may be a widespread manifestation of aging.
