Testosterone secretion in the rat in response to chorionic gonadotrophin: alterations with age.
It has been reported by others that both prevailing blood concentrations of testosterone and Leydig cell response to gonadotrophin (up to 1 h after injection) are reduced in the aged male rat. Although resting levels of plasma testosterone in our aged (24-26 months old) Sprague-Dawley rat are also depressed compared with young (3-4 months) or mature (12 months) animals of the same strain, subcutaneous injection with human chorionic gonadotrophin for 3 days restores secretory function, producing testosterone levels indistinguishable from those of similarly stimulated younger rats. In short term experiments, old rats did show a diminished testesterone secretory response to human chorionic gonadotrophin 1 h after a single intravenous injection, consistent with previous reports, but restoration of normal stimulated levels was observed by 2 h, and persisted up to 24 h. These findings differ from the demonstrated intrinsic testicular hyporesponsiveness to gonadotrophin of aged men, and probably represented a state of chronic understimulation of the aged rat Leydig cells, due to low prevailing levels of LH.
D000375:Aging; D000818:Animals; D001835:Body Weight; D006063:Chorionic Gonadotropin / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D051381:Rats; D013739:Testosterone / Q000097:blood*
D006063:Chorionic Gonadotropin; D013739:Testosterone