title: Unlabeled hemoglobin adducts of 4,4'-methylenebis (2-chloroaniline) in rats and guinea pigs.
abstract: The capacity of N-oxidized metabolites of 4,4'-methylenebis(2-chloroaniline) (MBOCA) to form hemoglobin (Hb) adducts was determined in vitro, and the formation of Hb adducts following in vivo administration of MBOCA was assessed with or without prior induction of cytochrome P-450 enzymes with phenobarbital or beta-naphthoflavone. Hb adduct formation was determined by electron-capture GLC of MBOCA as the heptafluorobutyryl derivative following mild acid hydrolysis of protein-bound MBOCA. The method was confirmed by gas chromatography-mass spectrometry with selected ion monitoring. N-hydroxy- and mononitroso-MBOCA, but not MBOCA itself, formed adducts to rat and human Hb in vitro in a dose-related manner. Binding was inhibited by cysteine and glutathione but not oxidized glutathione or methionine. Intravenous administration of as little as 0.04 mumol/kg N-hydroxy-MBOCA to rats resulted in measurable formation of MBOCA-Hb adducts (0.9 ng/50 mg Hb). Intraperitoneal administration of 0.5-50 mg/kg MBOCA to rats, and subcutaneous administration of 5-500 mg/kg MBOCA to rats and 4-100 mg/kg to guinea pigs resulted in dose-related formation of Hb adducts. MBOCA-Hb remained elevated in blood for greater than 10 weeks following a single subcutaneous dose in guinea pigs. Pretreatment of rats with phenobarbital induced microsomal benzphetamine N-demethylase (BND) activity and resulted in a small increase in in vitro N- and ortho-hydroxylation of MBOCA, but did not increase in vivo Hb adducts.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Pharmacology and Toxicology, Michigan State University, East Lansing 48824.
authors.forename: T H
authors.initials: TH
authors.lastname: Chen
authors.forename: B I
authors.initials: BI
authors.lastname: Kuslikis
authors.forename: W E
authors.initials: WE
authors.lastname: Braselton
mesh_terms: D000818:Animals; D001205:Ascorbic Acid / Q000494:pharmacology; D001571:Benzoflavones / Q000494:pharmacology; D003577:Cytochrome P-450 Enzyme System / Q000096:biosynthesis; D008401:Gas Chromatography-Mass Spectrometry; D006168:Guinea Pigs; D006454:Hemoglobins / Q000378:metabolism*; D008297:Male; D008753:Methylenebis(chloroaniline) / Q000378:metabolism*; D010634:Phenobarbital / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains
chemical_list: D001571:Benzoflavones; D006454:Hemoglobins; D008753:Methylenebis(chloroaniline); C011512:alpha-naphthoflavone; D003577:Cytochrome P-450 Enzyme System; D001205:Ascorbic Acid; D010634:Phenobarbital