THE RELATION OF AGE TO REACTIVITY IN THE REPRODUCTIVE SYSTEM OF THE RAT1,2

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Abstract
Equine gonadotrophin, testosterone propionate, and estradiol benzoate were injected into [female] and [male] rats for periods of 6 days beginning at birth, 4, 8, 12, 20, 30 or 50 days. Studies were made of the changes in wt. and histology of the gonads and accessory reproductive organs. Reactivity, as judged by increase or decrease in organ wts. in response to hormone treatment, was present between birth and 6 days of age in the testis, prostate, seminal vesicle, coagulating gland and uterus. Ovarian wt. response occurred in the period between 4 and 10 days of age. The initial % of change in wt. in re- sponse to stimulation was small in every organ but increased with age to a peak which was reached at 14 days for the testis, between 14 and 18 days for the prostate, and at 26 days of age for all other organs studied. Capacity to respond to stimulation histologically by precocious differentiation also developed gradually, and was found at younger ages than the greatest wt. increase.