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 < 0.0025) but similar levels of prolactin (P > 0.1) both before and 4 wk after castration. The in vitro release of LH, FSH, and free α-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 < 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 α/(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 α/(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. Moreover, the findings of reductions in the base-line in vitro molar secretory ratios of α/(LH + FSH) from cells of intact rats suggest that aging in the male rat may be associated with abnormally coordinated as well as quantitatively decreased α- and β-subunit production.
|Original language||English (US)|
|Journal||American Journal of Physiology - Endocrinology and Metabolism|
|State||Published - Jan 1 1985|
ASJC Scopus subject areas
- Endocrinology, Diabetes and Metabolism
- Physiology (medical)