Mechanisms of age-related changes in gonadotropin-releasing hormone receptor messenger ribonucleic acid content in the anterior pituitary of male rats

To determine the mechanism(s) of age-related changes in gonadotropin releas e from pituitary gonadotrophs in male rats, we measured the number of GnRH (gonadotropin-releasing hormone) receptor containing cells and expression o f GnRH receptor mRNA per cell in the anterior pituitary. An in situ hybridi zation procedure was performed using young (six months) and old (24-25 mont hs) Wister rats. An image analysis system was employed for the autoradiogra phic analysis, The number of pituitary cells increased during aging (approx imately 45%, p < 0.01). On the other hand, the number of GnRH receptor mRNA -containing cells decreased (approximately 25%, p < 0.05), The percentage o f these cells in old rats decreased to less than a half of that in young an imals (p < 0.01). GnRH receptor mRNA per cell in old rats was only 7% lower than in young (p < 0.01), These results suggest that loss of pituitary gon adotroph GnRH receptors and response is primarily due to the loss of gonado trophs, and that the death mechanism(s) are responsible for decreased stimu lation of Gn release during aging, (C) 1999 Elsevier Science Inc. All right s reserved.