Proceedings: Action of chronically administered oestradiol on the uterus of the rat

Abstract

Oestradiol induces increased synthesis of RNA and DNA in the uterus of ovariectomized rats. The effects of continuously administered oestradiol on nucleotide synthesis in the uterus of the rats are reported. Ovariectomized rats were given 2 Mug oestradiol-17 beta, subcutaneously, every 8 hr until autopsy at various times 1 to 7 days after the first injection of oestradiol. (3H) uridine or (3H) thymidine was administered intraluminally 15 min before beath. Uteri were processed for autoradiography. The number of labelled cells and the average number of grains/cell were counted. (3H) uridine labelling reached a peak at 6 to 54 hr and then decreased steadily thereafter. DNA synthesis was maximal at 48 hr in all regions and minimal at 144 hr. These results indicate that oestrogen caused maximum stimulation of RNA synthesis in the rat uterus at 30 and 48 hr respectively but activity was reduced thereafter. The uterine epithelium and stroma were hypertrophied and hyperplastic when RNA and DNA synthesis were minimal. This could be due to refractoriness of the specific target tissues to continued hormonal stimulation.