Thiol groups in proteins as endogenous reductants to determine glutathione-protein mixed disulphides in biological systems.

A novel method for glutathione-protein mixed disulphide (GSSP) determination, based on the use of protein sulphydryl groups as endogenous reductant and on the spectrophotometric determination of reduced glutathione, is described. The procedure is based on the observation that acid-precipitated proteins from different rat tissues rapidly release GSH from GSSP when brought to neutral pH. The basal GSSP content determined in rat liver, heart, lung, testis, spleen and brain corresponded to that reported in the literature and determined by more complex sample preparation or labor-intensive analytical procedures.