124 THE REGULATION OF CALCIUM TRANSPORT GENE EXPRESSIONS DURING PREGNANCY AFTER EXPOSURE TO OCTYLPHENOL AND BISPHENOL A

Abstract

Octylphenol (OP) is a degradation product of alkylphenol ethoxylates that are widely used to in rubber, pesticides, and paints. Bisphenol A (BPA) is an organic compound with two functional phenol groups and used to make polycarbonate plastic and epoxy resins, along with other applications. OP and BPA are known as endocrine disruptors that can induce inappropriate estrogenic action, and may disturb natural calcium metabolism. In the present study, the effects of OP and BPA on the calcium levels of serum and urine, and calcium transport genes were investigated in the duodenum and kidney of the pregnant mice. From 6.5 to 16.5 days post-coitus (dpc), 5 pregnant mice for each group were orally given with ethylestradiol (EE, 0.2 mg kg^–1 day ^–1), OP (15, 45, or 135 mg kg^–1 day^–1) or BPA (5 or 50 mg kg^–1 day ^–1) dissolved in corn oil. The duodenum, kidney, blood, and urine were obtained from the mice at day 18.5 of pregnancy. As a result, serum and urinary calcium levels were decreased by OP and BPA in a dose-dependent manner. The mRNA expression levels of calcium transport genes TRPV6 and CaBP-9k were decreased in the kidney after treatment with OP and BPA, while duodenal expression of TRPV6 was reduced by a high dose of BPA. The protein levels of these genes showed similar pattern with those of mRNA in the kidney and duodenum. The data were analyzed using a one-way ANOVA. P < 0.05 was considered statistically significant. Taken together, OP and BPA altered gene expressions associated with calcium transport in the pregnant mice, which may cause reduced serum and urine calcium levels. These results suggest that estrogenic actions of OP and BPA may lead to influence the calcium levels during pregnancy in the mice.