Reproductive Failure in Aged CBF1Male Mice: Interrelationships Between Pituitary Gonadotropic Hormones, Testicular Function, and Mating Success

Abstract

Circulating pituitary gonadotropins and testicular function were examined in aged CBF1 male mice using 2 experimental designs: a longitudinal analysis of 2-30 mo. old males and a direct comparison of weight-matched, sexually-active vs. sexually-inactive 24 mo. old males, all of whom were relatively robust. Measurements included serum concentrations of testosterone, follicle stimulating hormone [FSH] and luteinizing hormone [LH] gonadotropic responsiveness to castration, success in a 4-day mating test, testicular sperm content and reproductive organ weights. Longitudinal analysis showed progessive losses in mating success and sperm production between 18-30 mo., changes which were correlated with decreased levels of serum LH and testosterone but not with FSH. Direct comparison of robust, sexually-active vs. -inactive males provided a better design for identifying reproductive-specific effects of aging, as opposed to debilitative changes that are general to several supporting systems. Such comparisons in 24 mo. old CBF1 males suggest the existence of a subpopulation of mice in which reproductive failure is specifically correlated with a loss in LH episodic release.