Glutathione plus cytosol- and microsome-mediated binding of 1,2-dichloroethane to polynucleotides

Abstract

1,2-[1,2- 14C]Dichloroethane was metabolized by rat hepatic microsomes to products that irreversibly bound polynucleotides. The polynucleotides were then enzymatically hydrolyzed and the products separated by a high-performance liquid chromatograph (HPLC) equipped with an ODS or a SCX column. The products of microsome-mediated binding were identified in the HPLC eluate as 1, N 6 -ethenoadenosine to polyadenylic acid, 3, N 4 -ethenocytidine to polycytidylic acid, and two cyclic derivatives to polyguanylic acid. 1,2-[1,2- 14C]Dichloroethane was also metabolized in the presence of a glutathione (GSH)-cytosolic fraction and a polynucleotide. After enzymatic hydrolysis of the polynucleotide, the major peak of radioactivity was eluted from a Sephadex G-25 column in the salt volume which would exclude the presence of a product containing both GSH and a nucleoside. Chromatography by ODS-HPLC of the major peak from Sephadex G-25 indicated the presence of a GSH metabolite of 1,2-dichloroethane that did not contain a nucleoside. A similar hydrophilic peak was obtained for the hydrolysis products of polynucleotides from a glutathione plus cytosol incubation in which the polynucleotide instead of being added prior to the incubation was added after the incubation. The products of the glutathione plus cytosol metabolism of 1,2-[1,2- 14C]dichloroethane appear to be glutathione metabolites that coisolated with the polynucleotides rather than covalently bound adducts. In conclusion, covalently bound adducts were identified for microsomemediated binding of 1,2-dichloroethane to polynucleotides, while no evidence was obtained for glutathione plus cytosol-mediated covalent binding to polynucleotides.