EARLY EFFECTS OF TESTOSTERONE PROPIONATE INJECTED INTO 5 DAY OLD RATS

Abstract

ABSTRACT The present work deals with problems concerning a) factors influencing gonadal growth in rats during the first two weeks of life and b) the duration of action of 1.5 mg testosterone propionate (testosterone) injected subcutaneously into 5 day old rats (androgenized rats). Five groups of experiments were performed. The results were as follows: Injection of testosterone to 5 day old males reduced the growth of testes from 5 days after injection onwards. Semicastration at 1 day after birth was followed within 14 days by a compensatory hypertrophy of the remaining testis. Androgenization did not prevent a compensatory hypertrophy, but the weight of the remaining testis was reduced as compared with uninjected males. Unilateral ovariectomy at 1 day after birth failed to influence the weight of the remaining ovary recorded after 14 days. Observations on the occurrence of first oestrus and the type of vaginal smears were made in spayed rats receiving ovarian transplants in the anterior eye chamber when 15 days old. Either donors or recipients were androgenized. Testosterone had no effect on the ovaries. Intervals between injection of testosterone and vaginal opening decreased with advancing age both in intact and spayed rats. When testosterone was given to 5 or 18 day old rats, vaginal opening occurred after about 19 and 4 days, respectively. The response of mammary glands of spayed rats with or without androgenization indicated that a) testosterone produced an effect when the rats were about 10 days old and b) testosterone was effective for approximately 15 days.