Characterization of Chlorinated Adducts of Hemoglobin and Albumin Following Administration of Pentachlorophenol to Rats

Abstract

Five cysteinyl adducts (including one with multiple isomeric forms) of hemoglobin (Hb) and albumin (Alb) have been characterized in the blood of Sprague-Dawley rats following administration of pentachlorophenol (PCP). Three of these adducts were formed by multiple substitution reactions of tetrachloro-1,4-benzoquinone (Cl4-1,4-BQ) and its products, and two arose from reactions of tetrachloro-1,4-benzosemiquinone (Cl4-1,4-SQ) and tetrachloro-1,2-benzosemiquinone (Cl4-1,2-SQ). Adducts of tetrachloro-1,2-benzoquinone (Cl4-1,2-BQ) were not observed. Regarding adducts of Cl4-1,4-BQ and its products, specific structures were assigned to monosubstituted, disubstituted, and trisubstituted adducts of Hb and Alb following modification of rat blood with Cl4-1,4-BQ (0-45 microM) in vitro and after metabolism of PCP (0-40 mg/kg body weight) in Sprague-Dawley rats, in vivo. The formation of all adducts was linear over the ranges tested, with Alb adducts being more abundant than Hb adducts. The levels of the adducts measured were in the following order: monosubstituted > disubstituted > trisubstituted. The observation that Cl4-1,4-BQ can produce multisubstituted adducts with proteins suggests that protein-protein cross links may be formed, with inherent toxicological implications. Regarding adducts of the semiquinones (detected only in vivo), linear production of Hb and Alb adducts was observed with increasing dosage of PCP for adducts of both Cl4-1,4-SQ and Cl4-1,2-SQ. Higher levels of the semiquinone adducts were observed in Hb than in Alb, in contrast to the results with the quinone adducts. In a separate in vivo experiment (20 mg PCP/kg body weight), where animals were sacrificed at intervals up to 336 h postadministration, adducts were eliminated at rates which were comparable among the different adducts of a given protein.

Glutathione Conjugates of Ochratoxin a as Biomarkers of Exposure / Glutationski Konjugati Okratoksina A Kao Biomarkeri Izloženosti

“…OTA possesses a chlorophenolic group, and chlorophenols are well known to undergo oxidative dechlorination reactions to afford quinone/ hydroquinone redox couples (15,16). The hydroquinone metabolite (OTHQ, Figure 1) of OTA has been detected in the urine (17) and kidneys (18) of rats, and in human blood and urine samples (19).…”

Enrichment of cysteinyl adducts of human serum albumin

“…As a result, Cys34 has an unusually low pK a (<6.7 compared to about 8.0 - 8.5 for thiols in most other proteins and peptides) and exists primarily in the highly nucleophilic thiolate form [8]. Examples of the many chemical species that form adducts with Cys 34 include oxirane and quinone metabolites of benzene, naphthalene, and pentachlorophenol [9; 10; 11; 12; 13], nitrogen mustards [14], 4-hydroxy- trans -2-nonenal, 2-propenal, malondialdehyde, glyoxal, and other products of lipid peroxidation [15; 16; 17], metal ions such as Ag + , Hg 2+ , and Au + , and a host of drugs including auranofin, D-penicillamine, ethacrynate, and cisplatin (reviewed by [18]). Yet, although some HSA-Cys 34 adducts have been detected in studies of humans, the analytical matrix is complex and the levels of individual adducts have been very low (less than one in a million unadducted protein molecules [4]).…”

Fractionation of protein adducts in rats and mice dosed with [ 14 C]pentachlorophenol

“…Several studies have successfully applied Raney Ni to cleave cysteinyl adducts in various tissues, i.e., those of styrene 7,8-oxide styrene in blood proteins (Ting et al 1990;Rappaport et al 1993;Yeowell-O'Connell et al 1996), of benzoquinone in blood and bone-marrow proteins Rappaport et al 1996), of chlorinated quinones from PCP in blood and liver proteins (Lin et al 1999;Tsai et al 2001;Waidyanatha et al 1996), and of polychlorinated biphenyl quinones in liver and brain proteins (Lin et al 2000). By administering [ 14 C/ 12 C 6 ]PCP to animals along with the sequential counting scheme shown in Fig.…”

“…Two general mechanisms have been proposed for the toxic effects of quinones, namely covalent binding to macromolecules and generation of reactive oxygen species during redox cycling between the quinone and semiquinone forms (Bolton et al 2000;Bratton et al 1997;Monks and Lau 1992;O'Brien 1991). More specifically, quinone metabolites of PCP have been shown to covalently bind to macromolecules (Bodell and Pathak 1998;Ehrlich 1990;Lin et al 1999Lin et al , 2001avan Ommen et al 1986avan Ommen et al , 1986bvan Ommen et al , 1988Waidyanatha et al 1996;Witte et al 1985) and to produce oxidative damage to genomic DNA (Dahlhaus et al 1994(Dahlhaus et al , 1995(Dahlhaus et al , 1996Jansson and Jansson 1992;Lin et al 2001b;Naito et al 1994;SaiKato et al 1995;Umemura et al 1996Umemura et al , 1999Witte et al 2000).…”

“…Regarding specific covalent products, cysteinyl adducts of chlorinated quinones and two uncharacterized PCP adducts have been investigated in liver and/or blood from rats and mice following gavage administration of PCP (0-40 mg/kg body weight) (Lin et al 1997(Lin et al , 1999Waidyanatha et al 1996). Moreover, covalent binding of Cl 4 -1,4-BQ and Cl 4 -1,2-BQ has been quantified in microsomal incubations of [ 14 C]PCP (van Ommen et al 1986a(van Ommen et al , 1986b and of unlabeled PCP (Tsai et al 2001).…”