title: Ortho-substituted polychlorinated biphenyl (PCB) congeners (95 or 101) decrease pituitary response to thyrotropin releasing hormone.
abstract: Polychlorinated biphenyl compounds (PCBs) are global environmental contaminants that cause disruption of the endocrine system in humans and wildlife. Recently, we reported that acute exposures to ortho-PCB congeners 95 (2,3,6-2',5') or 101 (2,4,5,-2',5') causes changes in the performance of the hypothalamo-pituitary-thyroid (HPT)-axis in developing rats through mechanism(s) not yet clear. The functionality of the HPT-axis was evaluated by using the thyrotropin releasing hormone (TRH) test following acute exposure to PCBs 95 or 101. Weanling female rats received PCBs 95 or 101 intraperitoneally (ip) at 32 mg/kg for 2 consecutive days and synthetic TRH was given 48 h after the last dose. Serum thyroxine (T4) levels decreased following exposure to both the congeners. In PCB 95-treated rats, serum thyroid stimulating hormone (TSH) levels were elevated in response to TRH, but were only 40% of the control response to TRH. No significant changes were seen in serum prolactin (PRL), hypothalamic dopamine (DA), thyroid gland morphology, or epithelial cell proliferation. It is suggested that these congeners, interfere with the HPT-axis by causing a subnormal response of the pituitary and thyroid to TRH stimulation.
authors.affiliation: Department of Veterinary Biosciences, College of Veterinary Medicine, University of Illinois at Urbana-Champaign, 2001 S. Lincoln Ave., Urbana, IL 61802, USA.
authors.forename: Moazzam A
authors.initials: MA
authors.lastname: Khan
authors.forename: Larry G
authors.initials: LG
authors.lastname: Hansen
mesh_terms: D000818:Animals; D002455:Cell Division / Q000187:drug effects; D004396:Coloring Agents; D004298:Dopamine / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D005246:Feedback / Q000187:drug effects; D005260:Female; D007030:Hypothalamo-Hypophyseal System / Q000187:drug effects; D007031:Hypothalamus / Q000187:drug effects / Q000378:metabolism; D010902:Pituitary Gland / Q000187:drug effects*; D011078:Polychlorinated Biphenyls / Q000633:toxicity*; D011388:Prolactin / Q000097:blood; D018809:Proliferating Cell Nuclear Antigen; D051381:Rats; D017207:Rats, Sprague-Dawley; D013961:Thyroid Gland / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D013972:Thyrotropin / Q000097:blood; D013973:Thyrotropin-Releasing Hormone / Q000037:antagonists & inhibitors* / Q000494:pharmacology*; D013974:Thyroxine / Q000097:blood
chemical_list: D004396:Coloring Agents; D018809:Proliferating Cell Nuclear Antigen; C032904:2,2',3,5',6-pentachlorobiphenyl; D013973:Thyrotropin-Releasing Hormone; C009828:2,4,5,2',5'-pentachlorobiphenyl; D011388:Prolactin; D013972:Thyrotropin; D011078:Polychlorinated Biphenyls; D013974:Thyroxine; D004298:Dopamine