Demonstration of some of the physiological properties of rat relaxin.

Relaxin was extracted from the ovaries of pregnant rats. Material possessing uterine relaxing activity in vitro was eluted in three peaks from Sephadex G.50 columns. The 'G3 peak' material eluting in a position comparable to that of porcine relaxin inhibited myometrial activity of rats in vivo, improved the rate of rise of pressure of intrauterine pressure cycles in vivo, and, when administered to rats following progesterone and oestrogen priming, increased the distensibility of the cervix in vitro. This material also stimulated inter-pubic ligament formation in the mouse.. This rat relaxin material therefore exhibits biological actions in the rat similar to those previously assigned to porcine relaxin.