title: Polychlorinated biphenyls (PCBs) exert thyroid hormone-like effects in the fetal rat brain but do not bind to thyroid hormone receptors.
abstract: Polychlorinated biphenyls (PCBs) are ubiquitous environmental contaminants routinely found in human and animal tissues. Developmental exposure to PCBs is associated with neuropsychologic deficits, which may be related to effects on thyroid hormone (TH) signaling in the developing brain. However, PCBs may interfere with TH signaling solely by reducing circulating levels of TH, or they may exert direct effects on TH receptors (TRs). Therefore, we tested whether maternal exposure to a commercial PCB mixture, Aroclor 1254 (A1254), exerts effects in the fetal brain by one or both of these mechanisms. Dams were dosed daily with 0, 1, or 4 mg/kg A1254 from gestational day 6 (GD6) until they were sacrificed on GD16. A1254 significantly reduced circulating levels of triiodothyronine (T3) and thyroxine (T4) in pregnant rats but increased the expression of several TH-responsive genes in the fetal cortex, including neuroendocrine-specific protein A (NSP-A), RC3/neurogranin, and Oct-1. These findings are consistent with a direct action of PCBs on TRs. However, we did not identify parent PCB congeners or metabolites that bound to rat TRs isolated from hepatic nuclei. These findings indicate that PCBs can interfere with TH signaling in the fetal brain by direct actions on the fetus rather than by producing maternal hypothyroidism.
authors.affiliation: Biology Department, Molecular and Cellular Biology Program, Morrill Science Center, University of Massachusetts, Amherst, MA 01003, USA.
authors.forename: Kelly J
authors.initials: KJ
authors.lastname: Gauger
authors.forename: Yoshihisa
authors.initials: Y
authors.lastname: Kato
authors.forename: Koichi
authors.initials: K
authors.lastname: Haraguchi
authors.forename: Hans-Joachim
authors.initials: HJ
authors.lastname: Lehmler
authors.forename: Larry W
authors.initials: LW
authors.lastname: Robertson
authors.forename: Ruby
authors.initials: R
authors.lastname: Bansal
authors.forename: R Thomas
authors.initials: RT
authors.lastname: Zoeller
mesh_terms: D000818:Animals; D001921:Brain / Q000187:drug effects* / Q000196:embryology / Q000378:metabolism; D002540:Cerebral Cortex / Q000187:drug effects / Q000196:embryology / Q000378:metabolism; D020111:Chlorodiphenyl (54% Chlorine) / Q000494:pharmacology; D004785:Environmental Pollutants / Q000378:metabolism / Q000494:pharmacology*; D005260:Female; D005333:Fetus / Q000187:drug effects / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental / Q000187:drug effects; D007037:Hypothyroidism / Q000139:chemically induced / Q000378:metabolism; D008099:Liver / Q000378:metabolism; D008297:Male; D011078:Polychlorinated Biphenyls / Q000378:metabolism / Q000494:pharmacology*; D011247:Pregnancy; D051381:Rats; D017207:Rats, Sprague-Dawley; D011988:Receptors, Thyroid Hormone / Q000378:metabolism*; D013963:Thyroid Hormones / Q000378:metabolism*; D013974:Thyroxine / Q000378:metabolism; D014284:Triiodothyronine / Q000378:metabolism
chemical_list: D004785:Environmental Pollutants; D011988:Receptors, Thyroid Hormone; D013963:Thyroid Hormones; D014284:Triiodothyronine; D020111:Chlorodiphenyl (54% Chlorine); D011078:Polychlorinated Biphenyls; D013974:Thyroxine