Different regulation of the concentration of estrogen receptors in the rat liver and uterus following ovariectomy.

Data concerning the short- and longterm effects of ovariectomy on the levels of estrogen binding sites in the rat uterus and liver are presented. The information increases the understanding of the regulation of estrogen receptor synthesis. The circulating estrogen level is suggested to affect receptor synthesis in the uterus and liver differently. Shortly after gonadectomy (2--20 h), an elevation in the concentration of cytoplasmic binding sites in the uterus of 35% was observed, whereas no effect was seen in the liver cell. A longer period of time after ovariectomy (2--3 months) caused a reduction in the number of uterine receptor sites by 74%, whereas in the liver an increase of 84% was detected.