Abstract
It has been amply demonstrated that hypophyseal extracts containing the growth principle will prevent the gonad-stimulating action of hypophyseal or pregnancy urine extracts in immature or hypophysectomized rats (Smith, Evans, Reiss and Leonard). This inhibitory action was first ascribed by Evans and his coworkers to the growth hormone but later work led them to abandon their original thesis. Investigations along similar lines also indicated that the growth hormone is not the antagonistic principle. Results obtained on the study of this reaction constitute this report.
Sexually immature female rats were given 10 R.U. of pregnancy urine extract (Antuitrin S)† subcutaneously, which approximately doubled the weights of the ovaries in 5 days. Litter mates which were concurrently injected with pregnancy urine and extracts of beef and sheep pituitaries containing growth hormone (doses 1 cc. to 5 cc.) prepared after the method of Van Dyke, 1 failed to show the increase in weight of the ovaries. The repressing effect of the pituitary extracts upon the stimulated ovaries was also revealed by the infantile uteri and the closed vaginas of the young animals. For example, the average ovarian weight of 4 rats in one litter treated with Antuitrin S was 24.3 mg., the average of 4 littermates treated in the same manner plus the hypophyseal extract was 13.6 mg., a decrease of 44%. The uteri weighed 66.7% less and the vaginas of this latter group failed to open. In testing the various pituitary fractions for inhibition and in each of the subsequent tests, no less than 12 animals were used, 6 receiving the pregnancy urine and 6 receiving the combined injections. An ovarian weight of 15 mg. was taken for the uninjected controls which is the average size for immature rats of similar age in the colony.
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