Halogenated alkyl compounds are used extensively as herbicides, pesticides, and fire retardants, and many are employed as intermediates in manufacturing processes. Several of these compounds have been found to be genotoxic and cytotoxic. The overall objectives of the proposed research are to determine those structural features of halogenated alkyl compounds that are important determinants of genotoxicity and acute cytotoxicity, and to understand how halogenated alkyl compounds interact with tissue components to cause toxicity. Specifically, the mechanisms of toxicity of the nematocide and soil fumigant, 1,2-dibromo-3-chloropropane (DBCP) and some structural analogs will be investigated. The mechanism of DNA damage caused by DBCP in rat kidney, testes, and liver will be examined by characterization of its reactions with glutathione (GSH), and subsequent reactions of GSH conjugates with DNA. Synthesis of guanine adducts of DBCP-GSH conjugates will be attempted in order to obtain standards for the detection and quantification of these adducts in DNA hydrolysates from target and non-target tissues in the rat. In parallel, urinary metabolites of DBCP will be assayed by GC/MS/SIM with stable isotope standards. Changes in profiles of DNA adducts and urinary metabolites with treatments that are known to modulate tissue organ damage will be assessed to determine if they parallel. Methylated and other halogenated analogs of DBCP will be used to further assess a possible relationship between DNA damage and acute lethal cell injury in target tissues. Enanthiomers of DBCP will be synthesized to investigate steric effects on mutagenicity and DNA damage in testicular cells, and monodeuterated diastereomers of DBCP will be synthesized to determine reaction mechanisms of DBCP with GSH and DNA. Finally, biochemical mechanisms of DBCP and ethylene dibromide (EDB) cytotoxicity will be investigated in cultured hepatocytes to determine if the poly-(ADP-ribosyl)ation pathway and/or changes in intracellular Ca2+ concentrations are involved. Methylated and other analogs will serve as useful probes of these mechanisms in vivo. Overall these studies should provide new insights, into the mechanisms of toxicity of vicinal halo substituted alkanes.
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