Differential effect of estrogen on the production of cyclin B1, CDC2 p34 and C-FOS protein in rat uterus

Abstract

The uterine content of c-fos protein, cyclin B 1(cell cycle protein) and cdc2 p34(cyclin-dependent kinase) in immature and mature rats was determined using the enhanced chemiluminescence(ECL) western blot method. Cyclin B 1 was found predominantly in immature rat uterus and cdc2 p34 only in mature rat uterus. Several isoforms of c-fos oncogene protein were present in both mature and immature rat uteri. An additional immunoreactive c-fos protein with an estimated molecular weight of 28 kDa was found in mature rat uterus and was missing in immature uterus.

Uteri from ovariectomized rats treated with estrogen and/or ICI 182,780, an antiestrogen, were analyzed by ECL western blot, cdc2 p34 and the c-fos 28 kDa protein were found in estradiol-treated rat uteri and were not detected in uteri of control and ICI 182,780-treated animals; whereas Cyclin B 1 was absent in uteri from control and estradiol-treated ovariectomized animals. ICI 182,780 administered to estradiol-treated ovariectomized rats blocked the induction of cdc2 p34 and the c-fos 28 kDa protein in the uterus. The present results show that the production of the cell cycle factors, cyclin B 1, cdc2 p34 and c-fos, during rat uterine growth are under different regulatory controls. cdc2 p34 and c-fos 28 kDa protein are under the control of estradiol; whereas cyclin B 1 and the majority of the immunoreactive isoforms of c-fos are not influenced by this hormone.