THE RESPONSE OF THE PUBIC SYMPHYSIS OF THE MOUSE TO EXTRACTS OF PREGNANT RABBITSERUM AND PREGNANT SOW OVARIES AND ITS APPLICATION AS AN ASSAY METHOD1

Abstract

Mature, virgin female mice were used for the bioassay of a relaxative hormone present in crude extracts of pregnant rabbit serum (PRS) and pregnant sow ovaries (PSO). Following 7 days'' pretreatment with 1 [mu]g. estradiol 17-beta daily, a single dose of either extract produced significant separation of the pubic symphysis. The response was measured by means of X-ray photographs of the pelvis. A 2-fold increase in sensitivity to the hormone was observed when the estradiol priming period was lengthened to 23 days. Max. separation of the pubic symphysis of the mouse occurred within 16-24 hrs. after a single injn. of ovarian extract. Intact or castrated mice responded equally well. A statistical analysis of the assay data indicated that reliable quantitative assays were obtained. Lacking a standard powder, a provisional unit of activity (mouse unit) was defined as follows That amt. of relaxative hormone which will produce a mean increment of 0.65 mm. in the separation of the pubic symphysis, when given as a single injn. to a group of 6-8 mice pretreated with 1 [mu]g. of estradiol for 7 days.