ATTEMPT TO DIFFERENTIATE BETWEEN INDIVIDUAL GLUTATHIONE PEROXIDASES IN BIOLOGICAL SAMPLES

Routine determinations of glutathione peroxidases (GPx) still suffer f rom poor standardization and usually from lack of specification. The d ifferent types of glutathione peroxidases present in cellular homogena tes may be differentially estimated by their distinct substrate specif icities. Complex lipid hydroperoxides required for this approach, howe ver, are not generally available nor easily standardized due to their molecular heterogeneity and tendency to form micelles. We therefore de veloped a simple procedure for the differential estimation of the majo r cellular types of GPx, the cytosolic GPx (cGPx) and the phospholipid hydroperoxide glutathione peroxidase (PHGPx) taking advantage of the peculiar susceptibility of PHGPx to deoxycholate. It proved to reliabl y determine the activities of both purified cGPx and PHGPx, in mixture s thereof, and in homogenates of tissue samples (e.g., testes), and so me (e.g. ECV 304) but not all (e.g. THP-1) cultured cell lines. The me thod allows the differential estimation of cGPx and PHGPx, if the samp les do not contain further types of GPx.