Alkylation of Cellular Macromolecules by Reactive Metabolic Intermediate of DBCP

Abstract

Alkylating potential of DBCP on cellular macromolecules in vitro and in vivo was investigated using 14C-DBCP and male Wistar rats. In studies in vitro with rat-liver-microsome system, incorporation of DBCP-radiocarbon into TCA-and organic-solvents unextractable microsomal proteins was determined. The incorporation was dependent on incubation time, 14C-DBCP concentration, enzymatically active microsomes, NADPH, and oxygen, but it was not affected by sufficient puromycin to inhibit protein synthesis. Addition of SKF-525A, diethyldithiocarbamic acid, cysteine, or glutathione prevented the incorporation, and low concentration of 1, 1, 1-trichloropropane-2, 3-oxide, an inhibitor of epoxide hydrase stimulated the incorporation. When 14C-DBCP (20 mg/ kg) was orally administered to rats, TCA-and organic-solvents unextractable macromolecular residues were formed in rat tissues in parallel to the depletion of hepatic glutathione. Gel-fitration, protease digestion, and 2, 4-dinitrofluorobenzene treating of the liver homogenate showed an existence of radioactive proteins of which primary structure was radiolabeled. DNA isolated from the liver was also radiolabeled. From these results it was concluded that DBCP is oxidatively metabolized to reactive metabolic intermediate(s) by microsomal cytochrome p-450 system and covalently bind with nucleophilic sites of the cellular macromolecules in vitro and also in vivo. And epoxide was proposed as one of the reactive metabolic intermediate(s) responsible for protein alkylation by DBCP.

Review and Meta-analysis of Risk Estimates for Prostate Cancer in Pesticide Manufacturing Workers

“…organochlorines: for review, see [99,113]; triazines: for review, see [114][115][116][117][118][119][120][121][122][123]; for 2,4-D: [124][125][126]. For other pesticides, it is reported that mutagenicity and alterations of other cellular processes including protein metabolism and cell proliferation may contribute to their clastogenic and tumorigenic activity (chloroacetanilides: [127]; halogenated hydrocarbon nematocide-DBCP: [128][129][130][131][132]. In addition, as DBCP is also known to damage human male reproductive organs, it is plausible that it could contribute to the development of prostate cancer (for review, see [56]).…”

Metabolic activation of 1,2-dibromo-3-chloropropane: evidence for the formation of reactive episulfonium ion intermediates

“…Chronic administration of DBCP to animals has resulted in tumors of the nasal turbinates, forestomach, and liver (National Cancer Institute, 1980;Whorton & Foliart, 1983). Initial studies on the mechanism of DBCP bioactivation have proposed activation via the intermediacy of an electrophilic epihalohydrin (epichlorohydrin or epibromohydrin; Jones et al, 1979) which was proposed to bind irreversibly to tissue macromolecules (Kato et al, 1980). This suggestion was supported by the observation 'This work was supported by a grant from the National Institutes of Health (ES02728).…”

Correlation between Macromolecular Binding of DBCP-Metabolite and Pathogenicity of Necrosis

“…After the finding on the formation of organic-solvents unextractable radioactive residues in toxicologically target organs (liver, kidney, and testes) in rats dosed with radiocarbon-labeled DBCP, 17 we have been investigating the alkylating potential of the chemical in animals to elucidate its adverse effects. And in preceding papers18, 19 we have found that DBCP posseses a potential to bind covalently with nucleophilic sites of cellular macromolecules (proteins and DNA) in vitro and in vivo after an oxidative me-* Metabolic Fate of DBCP in Rats (Part 3) tabolic transformation by liver microsomal cytochrome p-450 enzyme systems.…”

“…Radioactive residues thus obtained were combusted to determine the radiocarbon covalently bound with the cellular macromolecules majorly consisted of proteins. 19 …”