title: 1-amino-3,7,8-trichlorodibenzo-p-dioxin: a specific antagonist for TCDD-induced myelotoxicity.
abstract: It was recently reported that suppression of murine bone marrow hematopoiesis is a very sensitive indicator for 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) toxicity (1). We report here that a structural analog of TCDD, 1-NH2-3,7,8-trichlorodibenzo-p-dioxin (NH2-TriCDD), is a specific and effective antagonist for TCDD-induced myelotoxicity and enzyme induction. When administered to mice or added directly into culture at a 100-fold excess, relative to TCDD, NH2-TriCDD completely abrogated the ability of TCDD to inhibit granulocyte-macrophage progenitor cells (CFU-C) formation, an indicator of hematopoiesis. Further, NH2-TriCDD inhibited TCDD-induced activation of cytochrome P1-450 monooxygenase activity. Studies designed to measure specific binding of TCDD to the cytosolic Ah receptor indicated that NH2-TriCDD effectively inhibited binding of TCDD to the receptor by acting as a competitive antagonist (Ki = 0.72 nM).
mesh_terms: D000818:Animals; D001853:Bone Marrow / Q000187:drug effects; D004147:Dioxins / Q000037:antagonists & inhibitors* / Q000494:pharmacology*; D005260:Female; D006410:Hematopoiesis / Q000187:drug effects*; D006412:Hematopoietic Stem Cells / Q000187:drug effects; D007700:Kinetics; D008099:Liver / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D000072317:Polychlorinated Dibenzodioxins / Q000031:analogs & derivatives / Q000037:antagonists & inhibitors* / Q000494:pharmacology* / Q000633:toxicity; D018336:Receptors, Aryl Hydrocarbon; D011955:Receptors, Drug / Q000378:metabolism; D013329:Structure-Activity Relationship
chemical_list: D004147:Dioxins; D000072317:Polychlorinated Dibenzodioxins; D018336:Receptors, Aryl Hydrocarbon; D011955:Receptors, Drug; C014981:1-amino-3,7,8-trichlorodibenzo-4-dioxin