SEX DIFFERENCES IN GROWTH OF RATS, AND THEIR MODIFICATION BY A SINGLE INJECTION OF TESTOSTERONE PROPIONATE SHORTLY AFTER BIRTH

Abstract

SUMMARY A single s.c. injection of 0·5 mg. testosterone propionate to rats aged 2 or 5 days affected development and subsequent activity of the reproductive tract, and somatic growth. As adults, females displayed prolonged vaginal oestrus with lack of ovulation and with uteri smaller than in control-injected animals likewise killed when in oestrus; males had smaller testes, seminal vesicles and ventral prostates. Body growth increased in treated females and decreased in males. Data on specific gravity and weights of heart, liver and kidneys, indicate that both the normal sex difference and the changes in weight due to early androgen administration are attributable to overall differences in size and not to specific differences in any particular body component. These effects of the steroid appear to be comparable to those noted after castration at an early age.