CHARACTERIZATION OF THE ANTERIOR PITUITARY FACTOR WHICH ANTAGONIZES GONADOTROPHINS1

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Abstract
The anterior pituitary contains a substance (or substances), tentatively called the “antagonist,” which, on intraperitoneal administration, reduces the ovarian response to simultaneously administered gonadotrophins. During purification of anterior pituitary hormones this factor has most consistently been associated with the gonadotrophic fractions and in particular with the interstitial cell stimulating hormone (ICSH). Evidence is here presented which indicates that antagonism is not, however, an intrinsic property of sheep ICSH but is due to an undetermined substance which follows closely during purification and is still present in preparations of ICSH with a minimal effective dose of 1 μg. The antagonistic properties characteristic of partially purified follicle stimulating hormone (FSH) have been shown to disappear on continued purification.