INTERACTION OF ESTROGENS ON UTERINE GROWTH*

Abstract

Relative effectiveness of estradiol-17B, estrone and estriol in the production of uterine growth was tested on castrated, adult rats. Animals 100 days old (200 g) were used 7 days after castration. The various doses of estrogens were dissolved in 0.1 ml sesame oil and injected subcutaneously daily for 3 days, with autopsy at the 72nd hour. Dosage-response curves based on increases in uterine wet weight showed estradiol to be about 10 times more effective than estrone. A maximal response of about 300 mg was obtained by a daily dosage of 1.0 ug of estradiol and by 10 ug estrone. Estriol was not only the least active of the 3 estrogens but was found incapable of stimulating maximal uterine growth in the 72-hr. period. Estriol in a dose of 0.1 ug decreased the growth-promoting action of estradiol and estrone when the hormones were given simultaneously. A maximal response to a given daily dose of estrogen was attained at about 72 hrs. and the weight of the uterus remained approximately the same when treatment was continued for 15 days. Uterine growth produced and maintained either by estradiol or by estrone or a combination of the 2 was reduced when estriol was added.