Identification of a reactive glutathione conjugate as a metabolite of SR-2508 in CHO cells.

Reaction between GSH and the hydroxylamine derivative of SR-2508 results in the formation of two stable conjugates identified as 2-amino-4-S-glutathionyl and 2-amino-5-S-glutathionyl imidazoles. These stable conjugates are apparently formed from a reactive derivative of the hydroxylamine that is sufficiently stable to be isolated after HPLC separation. The physical and chemical properties of this derivative are consistent with it being a GSH conjugate in which the glutathionyl residue is attached to the 2-amino nitrogen of the imidazole moiety through sulphur. With excess GSH, under physiological conditions, it forms a mixture of the two stable GSH conjugates. In CHO cells exposed to SR-2508 under hypoxic conditions, this unstable GSH conjugate has been detected and suggests the possibility of GSH functioning as a carrier of a toxic metabolite of 2-nitroimidazoles under certain conditions.