COMPARISON OF PROTEIN ANABOLIC PROPERTIES OF TESTOSTERONE PROPIONATE AND GROWTH HORMONE IN THE RAT

Abstract

Castration of adult male rats produced a slight increase in N excretion and a small drop in body wt. during the first few days followed by a period of slight N retention and gain in body wt. Hypophysectomy, on the other hand, produced a rapid and large loss in body wt. accompanied by a very marked extra excretion of N, which gradually returned to equilibrium. Injn. of testosterone propionate at 1 mg. day and growth hormone at 1.1 units/day into castrated male rats on constant food intake produced identical increases in body wt. and N retention for 14 days, then the effect of the androgen on body wt. ceased to persist while that of the growth hormone continued. Also, the N excretion of both groups of rats returned toward the pre-injn. level. On cessation of injns. a rebound or loss of N occurred in both groups of rats. Testosterone propionate at doses of 1-5 mg./day and a pellet of testosterone (0.33 mg./day) produced in the hypophysectomized male rat similar increases in body wt. and N retention. The effect on body wt. persisted for a much longer period than in the castrated rat while the N excretion decreased to a much lesser degree but as in the case of the castrated rat gradually returned to equilibrium on continuation of injns. and increased for several days on cessation of injns. Growth hormone produced a much greater effect on N retention and increase in body wt. in the hypophysectomized than in the castrated rat and also was more effective than the androgen. The N-retaining property of this hormone also did not persist but gradually returned to normal. The increase in body wt., however, was maintained at the "plateaued" maximum for the duration of the injns. On cessation of injns. a sharp drop in body wt. and an increase in N excretion occurred.