Ovulating-inducing activity of FSH in the rat

Ovine LH or FSH administered 44 hr after a priming dose of PMS induced ovulation inhypophysectomized immature rats. A well-characterized and highly specific LH antiserum (A/S) showing no cross reactivity with NIH FSH, TSH, GH or pr.olactin or with serum and tissue proteinextracts, was used to test the ability of NIH-FSH or LH-free FSH to cause ovulation. Theminimal effective dose (MEID) of LH A/S blocking ovulation induced by 10 ug LH was 3.0 ul per rat whereas that for blocking ovulation induced by FSH (100 ug) was 1.0 ul. While the MEID of the LH A/S for inhibition of ovarian weight gain was about 3 times greater than forinhibition of ovulation induced by LH, that for suppression of ovarian weight gain and inhibition of ovulation induced by FSH were the same. Incubation of FSH with variable amounts of LH A/Sfollowed by removal of the LH A/S with anti-rabbit gamma globulin resulted in preparations having no LH contamination as indicated by the double immunodiffusion test. The ovulation inducing capacity of this LH free FSH was negligible