Responses of Hypophysectomized Immature Female Rats to Mare Serum Hormone. ∗

Abstract

Summary and Conclusions

Cole 5 and Cartland and Nelson 6 reported their inability to secure evidence for the presence of more than a single principle in pregnant mare serum. However, Evans, et al., 7 have indicated that this material can be fractionated with ammonium sulphate into FSH and ICSH as tested in hypophysectomized rats in a 72-hour period, but the details of the tests were not. reported. It is well known that a varied ovarian response can be obtained with gonadotropins by altering the experimental conditions and the present experiments indicate the importance of dosage in the response elicited by mare serum hormone in hypophysectomized immature rats. In these experiments the predominant formation of thecal luteinization was observed with low doses of this material. Larger amounts of this hormone primarily caused the development of large vesicular follicles, whereas with a further increase of the dosage corpora lutea resulted. Large amounts of castrate urine extract also produced corpora lutea but this material produced only follicle stimulation in the absence of thecal luteinization in ovaries weighing as much as 80 mg. 8 Thus a definite difference in the gonadotropic activity of mare serum hormone and castrate urine extract can be cited as both materials were tested under identical experimental conditions.