Comparison of Conjugative Activity, Conversion of Bisphenol A to Bisphenol A Glucuronide, in Fetal and Mature Male Rat

We showed previously that orally administered bisphenol A (BPA) easily crosses the placental barrier and enters the fetus. However, BPA glucuronide transport and metabolism in the fetus was not studied. We examined the transport of orally administered BPA and BPA glucuronide into mature rat testis and fetus of pregnant rats. After administration of an oral dose of 10 mg BPA per kg body weight to pregnant female rats, BPA glucuronide in the fetus was not detected. BPA glucuronide does not easily pass through the placental barrier. One hour after oral administration of 10 mg BPA per kg body weight to mature male rats, approximately 90% of the BPA was present as BPA glucuronide in both blood plasma and testis. Although the concentration of free BPA in blood plasma decreased gradually, free BPA in the testis had increased slightly 8 h after administration. Eight hours after oral administration of BPA, BPA glucuronide gradually decreased in rat testis. In contrast, following oral BPA administration, blood plasma BPA glucuronide decreased to 55% of the maximum observed concentration after 3 h, but then increased to 100% of the maximum observed concentration after 8 h. These results suggest that BPA easily passes through the testicular barrier, is converted by UDP-glucuronosyltransferase to BPA glucuronide, and gradually breaks down to BPA by β-glucuronidase.