Maternal Exposure to Bisphenol A during Late Pregnancy Resulted in an Increase of Calbindin-D9k mRNA and Protein in Maternal and Postnatal Rat Uteri

Abstract

Abstract. It has been reported that Calbindin-D9k (CaBP-9k) is rapidly and strongly induced by environmental estrogenic compounds, possibly through estrogen receptors (ERα) in the uterus of mammals. CaBP-9k can be evaluated as an early gene marker for assaying estrogenic effects of putative environmental chemicals in the rat uterus. This study was undertaken to investigate CaBP-9k mRNA and protein expression in the postnatal rat uterus following maternal exposure to 17β-estradiol (E2) and bisphenol A (BPA) during the neonatal period. Treatment with a high dose of BPA (600 mg/kg body weight (BW) per day) resulted in a 3-fold increase in CaBP-9k mRNA expression for 3 days, while a single dose of E2 (40 µg/kg BW per day) induced 2-fold increase of this gene in the maternal uterus. In an agreement with maternal CaBP-9k mRNA, postnatal CaBP-9k mRNA in the uterus increased 4-fold when treated with BPA (600 mg/kg BW per day). In addition, treatment with increasing concentrations of BPA resulted in significant increases in CaBP-9k protein in the maternal rat uterus. It is of interest that increasing doses of BPA induced a significant ERα mRNA increase in the postnatal uterus. Furthermore, immunohistochemistry revealed that treatment with BPA induced CaBP-9k protein in the maternal uterus. We demonstrated that maternal exposure to BPA during late pregnancy induced CaBP-9k mRNA and protein in maternal and postnatal rat uteri. These results suggest that rapid absorption and distribution of environmental estrogenic compounds occurs in maternal and neonatal rat uteri and these chemicals can easily pass though the placenta during pregnancy to affect postnatal reproductive functions. Key words: Bisphenol A, Calbindin-D9k, Placental transfer, Postnatal (J. Reprod. Dev. 51: [499][500][501][502][503][504][505][506][507][508] 2005) albindin-D9k (CaBP-9k) and calbindin-D28k belong to a group of cytosolic calcium binding proteins [1]. CaBP-9k is a 9kDa cytoplasmic protein that binds to calcium with high affinity and is expressed predominantly in the mammalian uterus, intestine, and placenta [1,2]. The human CaBP-9k gene, which spans approximately 5.5 kb on the X-chromosome, was cloned and sequenced. It was reported to consist of 3 exons and to carry 4 A l u r ep e a t s [ 3 ] . H u m a n C aB P -9 k i s m o s t homologous to the porcine and bovine homologs (88.6%), followed by rat (78.5%) and murine CaBP9k (75.9%) [4]. In the rat uterus, it has been demonstrated that the CaBP-9k gene is highly regulated by estrogen (E2). CaBP-9k mRNA

Dietary Calcium and 1,25-Dihydroxyvitamin D3 Regulate Transcription of Calcium Transporter Genes in Calbindin-D9k Knockout Mice

“…In the present study, we examined the effect of dietary calcium and vitamin D3 on the expression of calcium-regulating genes in CaBP-9k KO mice. The calcium-binding protein CaBP-9k is expressed in the intestine, uterus, placenta, kidney, bone and pituitary glands of mammals [36][37][38][39][40][41]. Duodenal CaBP-9k is involved in active calcium absorption and is upregulated by the hormonal form of vitamin D and downregulated by dexamethasone, a synthetic glucocorticoid [42,43].…”

NTP‐CERHR expert panel report on the reproductive and developmental toxicity of bisphenol A

“…Hong et al (2005), sponsored by the Korea Research Foundation, investigated the effects of acute exposures to bisphenol A during late pregnancy on expression and protein level of calbindin-D 9k, a putative biomarker of estrogen activity, in the uteri of offspring and lactating rats on PND 5. Pregnant Sprague-Dawley rats were given free access to water and a diet of soy-free pellets in polycarbonate caging.…”

Early programing of uterine tissue by bisphenol A: Critical evaluation of evidence from animal exposure studies

“…The gene expression changes observed likely represent a short term, reversible response to BPA, given the short (1 day) interval between the last exposure and RNA analysis. In two other studies using the same high daily dose of BPA but different exposure windows, significant increases in uterine expression of estrogen regulated CaBP-9k protein and RNA were observed [58,63]. In one study pups were breast fed by dams exposed to BPA from day P1 to P5 and euthanized 24 hr after the last BPA injection [58], and in the second study pups were exposed to BPA in utero from E17 to E19 and euthanized on P5 [63].…”