Effects of in vivo estradiol administration on availability of rat uterine nuclear acceptor in measured in vitro.

Estradiol injected in vivo successfully completes for binding to uterine nuclear acceptor sites measured by the assay of Kon and Spelsberg (1). Such competition is time-and dose-dependent, with maximal inhibition (75%) 1 h after injection and at a dose of 10 micrograms of 17 beta-estradiol per 300 g of BW. Thus, this assay appears to accurately measure those uterine nuclear acceptor sites mediating estrogen action in vivo.