Dose and Time Dependency of Estrogen Effects on Bcl‐2 Family Members in the Uterus of Ovariectomized (OVX) Rats

Abstract

Changes in expression of Bcl‐2 family members in endometrium accompany hormone cycling during estrus and menstruation. We examined dose and time effects of estrogen on proteins of the Bcl‐2 family in rat uterine homogenates using Western blot analysis. Animals were injected with the vehicle sesame oil (SO) for 14days; SO for 10days followed by 2.5μg 17β‐estradiol (E2) for 4 days (SO+2.5/4d); 2.5μg E2 for 14 (2.5/14d) or 10μgE2 for 14 (10/14d) days. All treatments increased plasma E2 levels over control with 2.5/4d and 2.5/14d E2 resulting in levels similar to proestrus levels and 10/14d E2 resulting in levels 2.5 times higher. All E2 treatments increased uterine weight relative to vehicle. Characterization of the Bcl‐2 antibody revealed an increase in the 26KDa Bcl‐2 band with all E2 regimens, but another band at about 22KDa, not previously reported, was also increased. Preabsorption of the Bcl‐2 antibody with blocking peptide (against which it was raised) eliminated immunoreactivity of the 26KDa band. All E2 regimens significantly increased Bax and Bad immunolabeling over vehicle. Our data are important in understanding the effects of different hormone therapies in the uterus.