The effect on male rats of the simultaneous administration of male and female sexual hormones and the relation to the assay of the hormones

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Abstract
Rats (73), belonging to 16 litters, were injected for 7 or 21 days with preparations of testicular hormone, alone or in combination with estrin. The comb-growth method does not assay the whole sexual activity of male hormone preparations, while this is given by the assay on the prostate with seminal vesicles of castrated rats. The addition of estrin to testicular hormone injections greatly increased the wt. of the seminal vesicles and (more particularly in the 7-day expts.) caused only a slight, if any, increase in the weight of the prostate, penis and preputial glands. An alteration in the method of assay previously described and in the definition of the rat unit is therefore suggested, namely, that the % change in wt. of the prostate alone be used for the assay of the hormone "promoting comb-growth," and that of the prostate and seminal vesicles weighed together for the assay of "the whole [male] sexual activity" of the sexual hormone preparations. For this latter assay the changes in the wt. of the seminal vesicles in relation to the changes in the wt. of the prostate are also important. This alteration in the method causes no significant change in the number of R.U. in purified testicular hormone preparations, but eliminates those produced by additional sexual activity (e.g., estrin) in less purified preparations. The rat unit suggested is the min. daily dose, which when injected twice a day in half doses, during 7 consecutive days, into at least 3 litters of rats castrated before the 30th day after birth, will produce an av. increase of 40% in the wt. of prostate alone (for the assay of "comb-growth hormone") or in the wt. of the prostate with seminal vesicles (for the assay of the "whole [male] sexual activity") as compared with the av. wt. of the respective organs in the uninjected litter mates. The male and female hormones in the male organism are not sexual hormones only, but hormones with manifold effects on other important functions and organs. For ascertaining the other properties of testicular hormone preparations, in addition to the assay of sexual activity, rats castrated for not less than 70 days and injected with suitable doses for not less than 21 days are best to use. The effect of testicular hormone of increasing the wt. of the liver and kidneys was corroborated in these exps. Besides the effect on the sexual organs, the addition of estrin to testicular hormone injections was followed by a decreased gain in body wt. and fat deposition, an acceleration in the speed of involution of the thymus, an increased hypertrophy of the hypophysis, and a slight increase in the wt. of the kidneys.

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