title: The thyroid disruptor 1,1,1-trichloro-2,2-bis(p-chlorophenyl)-ethane appears to be an uncompetitive inverse agonist for the thyrotropin receptor.
abstract: In this study, we aimed at establishing whether two previously identified thyroid disruptors, the insecticide 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane (DDT) and Aroclor 1254 (a complex mixture of polychlorinated water), may inhibit thyrotropin (TSH) receptor (TSHr) activity. DDT and Aroclor 1254 were shown to inhibit both the basal and bovine TSH (bTSH)-stimulated accumulation of cAMP in Chinese hamster ovary (CHO)-K1 cells stably transfected with the TSHr. Furthermore, both DDT and Aroclor 1254 did indeed prevent cAMP accumulation, as induced by the constitutive activity of a point mutant TSHr(I486M) transiently transfected in African green monkey kidney fibroblast (COS)-7 cells. Neither trypsin digestion of the extracellular domain (ECD) nor deletion of the ECD in a mutant TSHr trunk transiently transfected in COS-7 cells counteracted the inhibitory activity of DDT and Aroclor 1254. DDT exerted a weak inhibitory activity against forskolin in both CHO-K1 and COS-7 cells, whereas it was nil against the agonists dopamine and 5'-(N-ethyl-carboxamido)-adenosine (NECA) in CHO cells stably transfected with the dopamine D1 receptor and in COS-7 cells transiently transfected with the adenosine type 2a receptor (A2a) receptor. Furthermore, DDT was inactive against the stimulation by isoproterenol of the endogenously expressed beta2 adrenergic receptor in COS-7 cells. Conversely, Aroclor 1254 inhibited completely forskolin activity in CHO-K1 cells but not in COS-7 cells. Furthermore, it did not prevent accumulation of cAMP as induced by NECA in A2a transfected cells. The analog of DDT, diphenylethylene, was inactive against bTSH-induced increase in cAMP in CHO-K1 cells stably transfected with the TSHr. We interpreted these results as indicating that DDT and possibly Aroclor 1254 may have an uncompetitive inverse agonist activity for the TSHr.
authors.affiliation: Department of Neurosciences, Centre of Excellence for the Study of Damage to the Nervous and Endocrine Systems Produced by Environmental, Alimentary, and Pharmacological Agents, University of Pisa, Pisa, Italy.
authors.forename: Mario
authors.initials: M
authors.lastname: Rossi
authors.forename: Antonio
authors.initials: A
authors.lastname: Dimida
authors.forename: Maria Teresa
authors.initials: MT
authors.lastname: Dell'anno
authors.forename: Maria Letizia
authors.initials: ML
authors.lastname: Trincavelli
authors.forename: Patrizia
authors.initials: P
authors.lastname: Agretti
authors.forename: Franco
authors.initials: F
authors.lastname: Giorgi
authors.forename: Giovanni U
authors.initials: GU
authors.lastname: Corsini
authors.forename: Aldo
authors.initials: A
authors.lastname: Pinchera
authors.forename: Paolo
authors.initials: P
authors.lastname: Vitti
authors.forename: Massimo
authors.initials: M
authors.lastname: Tonacchera
authors.forename: Roberto
authors.initials: R
authors.lastname: Maggio
mesh_terms: D019830:Adenosine-5'-(N-ethylcarboxamide) / Q000494:pharmacology; D000262:Adenylyl Cyclases / Q000378:metabolism; D000818:Animals; D001559:Benzhydryl Compounds; D016466:CHO Cells; D019556:COS Cells; D002522:Chlorocebus aethiops; D020111:Chlorodiphenyl (54% Chlorine) / Q000494:pharmacology; D005576:Colforsin / Q000494:pharmacology; D006224:Cricetinae; D000242:Cyclic AMP / Q000378:metabolism; D003634:DDT / Q000494:pharmacology*; D010636:Phenols / Q000494:pharmacology; D011989:Receptors, Thyrotropin / Q000037:antagonists & inhibitors* / Q000502:physiology; D013972:Thyrotropin / Q000494:pharmacology; D000098826:Bisphenol A Compounds
chemical_list: D019830:Adenosine-5'-(N-ethylcarboxamide); D000262:Adenylyl Cyclases; D001559:Benzhydryl Compounds; D020111:Chlorodiphenyl (54% Chlorine); D005576:Colforsin; D000242:Cyclic AMP; D003634:DDT; D010636:Phenols; D011989:Receptors, Thyrotropin; D013972:Thyrotropin; C006780:bisphenol A; D000098826:Bisphenol A Compounds