AJP - Endocrinology and Metabolism, Vol 249, Issue 2 145-E151, Copyright © 1985 by American Physiological Society
Decreased in vitro secretion of LH, FSH, and free alpha-subunits by pituitary cells from old male rats
M. R. Blackman, A. Mukherjee, P. D. Tsitouras and S. M. Harman
Various in vivo and in vitro pituitary-Leydig cell functions were examined
in mature (5-8 mo) vs. old (22-25 mo) male Wistar rats. Old rats exhibited
decreased serum concentrations of testosterone, luteinizing hormone (LH),
and follicle-stimulating hormone (FSH) (P less than 0.0025) but similar
levels of prolactin (P less than 0.01) both before and 4 wk after
castration. The in vitro release of LH, FSH, and free alpha-subunits was
measured in primary cultures of dispersed anterior pituitary cells from
both intact and castrated rats. During 48 h of incubation, basal secretion
rates of the glycoproteins were decreased (P less than 0.001) from cells of
both intact and castrated old rats. After stimulation with LH-releasing
hormone (LRH) in single (10(-8) M) or multiple (10(-10) - 10(-7) M) doses,
the total amounts of the glycoproteins secreted were also less from cells
of both intact and castrated old rats. However, repeated measures analysis
of variance revealed age-related hyporesponsivity to LRH stimulation only
for LH secretion by cells from intact rats. The basal molar ratios of
alpha/(LH + FSH) secreted by cells from intact but not castrated old rats
were lower than those from cells of the corresponding mature rats.
Moreover, after LRH stimulation (10(-10) - 10(-7) M), molar secretory
ratios of alpha/(LH + FSH) decreased from cells of intact mature rats but
increased from cells of intact old rats. These in vitro data suggest that
the reduced serum LH and FSH levels in intact and castrated old male rats
result in part from decreased secretion of these glycoproteins.(ABSTRACT
TRUNCATED AT 250 WORDS)
