VOLUNTARY EXERCISE INCREASES GONADOTROPIN-SECRETION IN MALE GOLDEN-HAMSTERS

To determine the effect of voluntary exercise and food restriction on reproductive hormone secretion, 48 adult male hamsters were placed in cages with (EX) or without (SED) running wheels. One-half of the anima ls in each exercise group was fed ad libitum, and the other half was f ood restricted to reduce their body weight to 90 g over 4 wk. After 10 wk, the EX ad libitum-fed group had much larger testes and much highe r serum follicle-stimulating hormone and testosterone levels than the other three groups, but these values in the EX food-restricted hamster s were similar to those in the SED food-restricted group. In experimen t 2, 20 adult male hamsters were castrated and later implanted with si licone rubber capsules containing testosterone. Two weeks after implan tation of the capsules, the serum follicle-stimulating hormone levels were higher in the EX than in the SED group of testosterone-treated ha msters, but not in animals receiving blank capsules. These data sugges t that exercise increases gonadotropin secretion by inhibiting the neg ative feedback of testosterone.