You are here:
EFFECTS ON HEPATIC GENE EXPRESSION IN MALE RATS ADMINISTERED PBDES IN HOUSEHOLD DUST
Citation:
RICHARDSON, V., H. HAKK, J. J. DILIBERTO, AND L. S. BIRNBAUM. EFFECTS ON HEPATIC GENE EXPRESSION IN MALE RATS ADMINISTERED PBDES IN HOUSEHOLD DUST. Presented at Society of Toxicology Annual Meeting, Charlotte, NC, March 25 - 29, 2007.
Description:
Studies show that polybrominated diphenyl ethers (PBDEs) decrease thyroid hormone concentrations via induction of hepatic uridinediphosphate-glucoronosyltransferase (UGTs) and transthyretin (Ttr) binding. Because PBDEs exhibit endocrine disrupting properties and are present in human tissue, sources of human exposure are of increasing interest. Our laboratory has found that PBDEs fed to adult male rats in dust (NIST Standard Reference Material 2585) or an oil vehicle are equally bioavailable. This study examines the effects of PBDEs in household dust through their ability to induce genes involved in thyroid hormone disruption. Adult male Sprague-Dawley rats were fed either household dust at 319 or 1851 ng PBDEs/day or peanut oil containing 20 PBDEs at 181 or 906 ng PBDEs/day for 21 days. On day 22, livers were taken for gene expression analysis using real-time RT-PCR. Hepatic Cyp1a1 mRNA was unchanged in rats fed PBDEs in oil, but was increased 2 and 3-fold in the 319 and 1851 ng PBDEs/day dust treatment groups, respectively. Exposures to 181 ng PBDEs/day in the oil vehicle had no effect on hepatic Cyp2b1 mRNA. Increases in hepatic Cyp2b1 mRNA were seen with 906 ng PBDEs/day in oil, and in both dose levels in dust (319 and 1851 ng PBDEs/day), by 4, 2, and 3-fold, respectively. Hepatic Cyp2b2 mRNA was unchanged in both dust and oil treatment groups of 319 and 181 ng PBDEs/day, respectively; whereas, Cyp2b2 mRNA increased 5 and 3-fold in the 1851 and 906 ng PBDEs/day of the dust and oil treatment groups, respectively. There was no change in hepatic Ugt1a1, Ugt1a7, Ugt2b, or Ttr mRNA. This study shows that household dust is equally as effective as a PBDE oil mixture through its induction of CYP2b2 mRNA expression, but the administered concentrations may not be sufficient for thyroid hormone disruption. The observed effects on CYP1A1 mRNA are likely due to other polyhalogenated aromatic compounds found in the household dust. (This does not necessarily reflect USEPA policy).