MODIFICATION BY RELAXIN OF THE RESPONSE OF THE REPRODUCTIVE TRACT OF MICE TO OESTRADIOL AND PROGESTERONE

SUMMARY A histological and histochemical study has been made of the effect of relaxin in modifying the action of oestradiol and progesterone on the reproductive tract of female mice. Special attention was paid to the cytoplasmic nucleic acids in relation to growth changes, and to alterations in glycogen and other polysaccharides, and in alkaline phosphatase activity. In the uterine horn, relaxin augmented the action of oestradiol on myometrial glycogen and alkaline phosphatase activity and on oedematous transformation of the endometrial stroma. The histochemical reactions of the mucopolysaccharide deposited in the altered stroma are discussed. Progesterone partly or completely inhibited the synergistic action of the other two hormones on myometrial glycogenesis and on oedematous changes in the endometrium, but not on alkaline phosphatase activity in myometrium and endometrium. Relaxin + oestradiol (but not oestradiol alone) partly prevented the depressing effect of progesterone on alkaline phosphatase activity in the myometrium and luminal epithelium. In the vagina, oestradiol and relaxin had a synergistic action on cellular hypertrophy and keratinization of the epithelium, and relaxin partly overcame the mucifying action of progesterone. Relaxin appeared to increase alkaline phosphatase activity in the lamina propria. No hormonally controlled mucopolysaccharides were detected in the cervical tissues, and the techniques have not provided a satisfactory explanation of the relaxin-induced softening of the cervix.