COMPARISON OF THE DELIVERY OF REDUCED GLUTATHIONE INTO P388D(1) CELLSBY REDUCED GLUTATHIONE AND ITS MONOETHYL AND DIETHYL ESTER DERIVATIVES

The effect of reduced glutathione, reduced glutathione monoethyl eater and reduced glutathione diethyl ester on the cellular concentration o f reduced glutathione and cysteine in P388D(1) macrophages in vitro, a nd the cellular and extracellular de-esterification of reduced glutath ione esters, was investigated. At 1 mM reduced glutathione derivative, only reduced glutathione diester markedly increased the cellular conc entration of reduced glutathione. There was little delivery of reduced glutathione monoethyl ester into the cells. Reduced glutathione, and monoethyl and diethyl ester derivatives all increased the cellular con centration of cysteine; reduced glutathione diethyl ester also increas ed the cellular concentration of gamma-glutamylcysteine. Reduced gluta thione esters were de-esterified intracellularly where the diester was rapidly converted to the monoester. The diester was also converted to the monoester extracellularly by interaction with cell surface estera ses and by a much slower spontaneous hydrolysis. This indicates that t he diester of reduced glutathione was a much more effective vehicle fo r delivery of reduced glutathione into cells than the monoester. Reduc ed glutathione diester also increased the cellular concentrations of c ysteine and gamma-glutamylcysteine, suggesting that de novo synthesis of reduced glutathione was also stimulated.