Two Gonadotropic Substances in Mare Serum. ∗

The finding by Cole and Hart 1 that there is no relationship between the activity of mare serum when administered alone and its activity when combined with pituitary synergist,† led them to believe that there are two gonadotropic substances in mare serum. More convincing evidence is now at hand. We have been able to make potent pregnancy serum completely ineffective when given alone without destroying its synergistic properties. This has been accomplished by several diverse methods. After treatment with H₂S and subsequent incubation at 37°C., the serum when given alone has no effect on the ovaries of immature rats, but when this serum is combined with pituitary synergist, marked augmentation occurs as is shown in Table I.

We interpret this as meaning that one substance has been destroyed by this treatment. The substance destroyed was capable of affecting the ovary either alone or in conjunction with the luteinizer remaining in the serum after treatment.

We have attempted to separate the 2 hormones from mare serum without destruction of either as has been done so successfully with the pituitary by Fevold and Hisaw. 3 They have shown that the pituitary contains 2 gonadotropic substances, a follicle-stimulator and a luteinizer. According to them the follicle-stimulating hormone will give a moderate response consisting of follicular development when given alone and the luteinizer gives no increase in ovarian weight, whereas if the 2 are combined the response is augmented. By Fevold's method, as well as by the method just described, we have succeeded in obtaining fractions of mare serum which behave similarly to pituitary luteinizer; i. e., the fraction when administered alone gives no response but if united with pituitary synergist, the response of the latter is augmented. This is shown in Table II.

We were also able to effect a crude concentration of the luteinizing substance by salting out, a method suggested by the work of Goss and Cole. 4