FURTHER CONSIDERATIONS OF THE PROPERTIES OF THE GONAD-STIMULATING PRINCIPLE OF MARE SERUM

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Abstract
The gonad-stimu-lating hormone of mare serum, injected into 7 immature [male] rats, produced marked responses in the seminal vesicles and prostate; approximately doubled the size of the testes, enlarged the tubules of the testis, and increased the amount of interstitial tissue. In 16 mature [male][male] on a normal diet it produced no marked changes in the reproductive organs, although there was evidence of increased secretory activity in the prostate and seminal vesicles. In 5 mature [male][male] on a protein-deficient diet there were responses in the prostate and seminal vesicles comparable to immature rats but the response of the testes was less conspicuous. Impotency in these low-protein rats was temporarily cured by the injection of the hormone. On a low-protein diet [male] rats became impotent after 2-3 mos. Serum from pregnant mares injected subcutaneously restored potency within 3-4 days to 8 of the 9 [male] rats on low-protein diet. The immature [female] rat is the most convenient test animal for assay of the gonad-stimulating hormone in mare serum. A rat unit of the gonad-stimulating hormone of mare serum is the amt. which will produce, in a group of 6 rats, an average of from 3-10 mature follicles or corpora for each immature [female] rat tested and autopsied 5 days after the injection and half of which amt. will fail to consistently produce a vaginal smear of estrum in another group of 6 rats. Larger doses result in the production of large numbers of corpora lutea atretica. Exps. on 64 [female] rats 21, 25 and 28 days old indicated that the no. of ovula-tiqns produced by injection of the gonad-stimulating principle of mare serum approaches that of the first normal estrum. Data are appended regarding the reaction of the [female][female] of other spp. to the hormone. The hormone as it occurs in serum is relatively stable in acid and alkali (pH 2-10) and is not easily destroyed by oxidation or by pepsin.