Re-evaluation of protein-bound glutathione in rat liver

The extent of intracellular glutathione binding to proteins through a disulfide linkage in rat liver was examined quantitatively. The content of glutathione associated with the acid-precipitable fraction and releasable on borohydride treatment was 0.024 +/- 0.016 mumol/g liver, which accounted for less than one per cent of the total glutathione (6-7 mumol/g liver) in the liver of fed rats. Most of the thiol (2-4 mumol/g liver) liberated from liver proteins into the acid-soluble fraction on borohydride reduction in the presence of guanidine hydrochloride was not glutathione but was proteinaceous in nature. The amounts of thiols liberated per g of liver were similar in fed, fasted, and dibutyryl-3',5'-cyclic AMP-treated rats.