A COMPARISON OF THE RESPONSE OF THE PUBIC SYMPHYSIS OF THE MOUSE AND GUINEA PIG TO EXTRACTS OF PREGNANT SOW OVARIES1

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Abstract
Relaxin-containing extracts from ovaries of pregnant sows were compared for their effectiveness in producing pelvic relaxation in mice and guinea pigs. Material concd, on the basis of the guinea pig assay was only slightly effective in the mouse as shown by roentgenographic measurement of pubic separation. Conversely, material coned, in respect to assay in the mouse contained less than 5% of the original guinea pig activity. When partially purified relaxin (guinea pig assay) was tested in the mouse, an atypical dose-response curve of low slope and high variability was observed. Use of different routes of admn., and addition of adjuvants (gelatin, alum) to prepns. of high specific guinea pig activity failed to restore activity for the mouse. The 2 types of relaxative hormone extracts were similar in resistance to heating and with respect to inactivation on exposure to cysteine. However, 6 [image] urea soln. inactivated a mouse-active extract but did not diminish guinea pig activity. It is suggested that the mouse-active fraction may represent the binding of relaxin to a less soluble, more slowly mobilized carrier molecule.