Estrogen receptor α pathway is involved in the regulation of Calbindin-D9k in the uterus of immature rats

Abstract

It has been demonstrated in our previous studies that Calbindin-D9k (CaBP-9k) is a potent biomarker for screening estrogen-Like chemicals in the rat model. Although treatments with 17beta-estradiol (E2) and endocrine disrupting compounds resulted in the up-regulation of uterine CaBP-9k, the mechanism of CaBP-9k induction by these compounds through two subtypes of estrogen receptors (ERα and ERβ) is unclear. Thus, in the present study, immature rats were treated with propyl pyrazole triol (PPT, an ERα-selective ligand), diarylpropionitrile (DPN, an ERβ-selective ligand), E2, or dimethyl sulfoxide (DMSO, a vehicle control) for three days in order to clarify which subtype of ER is involved in the uterine CaBP-9k induction. Following injection with these ER ligands, uterine CaBP-9k expression was analyzed by Northern blot and immunoblot assays. Uterine CaBP-9k expression is mainly mediated by PPT in a dose- and time-dependent manner in immature rats, whereas no significant alteration of the uterine CaBP-9k gene was observed after DPN treatment. In addition, an estrogenicity of PPT in inducing CaBP-9k expression was completely blocked by the anti-estrogen ICI 182,780, implying that uterine CaBP-9k is solely induced by ERα. A single treatment with PPT rapidly increased the protein levels of ERα and PR, an E2-mediated gene, in these tissues. Taken together, these results indicate that uterine CaBP-9k is induced by E2 and endocrine disrupting chemicals via the ERα pathway, but not ERβ, in the uterus of immature rats. © The Author 2005. Published by Oxford University Press on behalf of the Society of Toxicology. All rights reserved.