Biotransformation of some pyrazole derivatives to glutathione conjugates in rat liver subcellular fractions.

During incubation of antipyrine, but not amidopyrine, 4-aminoantipyrine and 4-leucylaminoantipyrine, with rat liver microsomaland cytosol fractions in the presence of NADPH-generating system a reactive metabolite, which binds with glutathione is formed. The chemical nature of the metabolically activated intermediate is not known; it is suggested that the putative reactive metabolite responsible for this binding could be an epoxide.