Transport of glutathione, as gamma-glutamylcysteinylglycyl ester, into liver and kidney.

Abstract

Administration of y-glutamylcysteinylglycyl monomethyl (or monoethyl) ester to mice leads to substantial increases in the levels of glutathione in the liver and kidney. Mice depleted of glutathione by treatment with buthionine sulfoximine, a potent inhibitor of y-glutamylcysteine synthetase, exhibited about a 4-fold increase in liver and kidney glutathione levels after administration of glutathione monomethyl ester. This ester also prevented the marked decline in liver glutathione level found after giving mice acetaminophen, and it protected mice from toxicity due to this compound. The findings indicate that the monomethyl and monoethyl esters of glutathione are transported into 'cells and hydrolyzed to glutathione. Such esters may be useful in experimental work on glutathione metabolism and function and may provide a relatively safe method for protecting cells against damage by toxic compounds, oxygen, and radiation.Several studies have shown that intracellular glutathione (GSH) is of major importance in protecting' cells against damage by toxic compounds, reactive oxygen compounds, and radiation (1-3). For this reason there has been interest in the factors that influence intracellular GSH synthesis and especially in ways of increasing cellular levels of GSH. Although the availability of cysteine may be a limiting factor in GSH synthesis, administration of this amino acid does not always lead to substantially increased GSH levels; cysteine is rapidly metabolized and it is also toxic, possibly in part because of its extracellular effects. Administration of compounds that are transported and converted intracellularly into cysteine, such as L-2-oxothiazolidine-4-carboxylate (4,5), are useful in increasing cellular GSH. Another promising approach for increasing kidney GSH levels is administration of y-glutamylcysteine (and related compounds), which are transported and stimulate GSH synthesis by providing a substrate for GSH synthetase (6). The possibility that administration of GSH itself might-lead to increased cellular GSH levels has also been considered. Recent studies on the metabolism of GSH indicate that GSH-is transported out of many cells, and that such export is a discrete step in GSH metabolism (2, 7,8). One might think that GSH export would'be reversible, but this does not seem to be the case. Although it is possible that some cells may take up intact GSH, there is as yet no conclusive evidence for transport of GSH into cells. Thus, the repletion of intracellular GSH in human lymphoid cells by exogenously supplied GSH was found to involve extracellular degradation of GSH, uptake of the products, and intracellular synthesis (9). The apparent uptake of GSH in the basolateral circulation of the kidney is evidently explained by cleavage of GSH to its constituent amino acids (10). No evidence for GSH uptake by the liver was obtained in studies on rats (11), and the moderate increase in kidney GSH levels observed after administration of GSH to mice may be explained by formation and transport of y-glut...

Nucleotide Depletion Due to Reactive Oxygen Metabolites in Endothelial Cells: Effects of Antioxidants and 3-Aminobenzamide

“…We observed only partial but dose-dependent prevention of nucleotide dcplction by GSH and very little cffcct on the leakage of nuclcotides into the culture medium. GSH is poorly transported into cndothelial cclls (26,27). and it may act as a scavenger of frce radicals (2.…”

Glutathione is required for intestinal function.

“…Mice (male; 34-38 g, Swiss-Webster from Taconic Farms) were maintained on Purina Chow. BSO (1,20,21), L-buthionine sulfone (21), and GSH monoethyl esterY2H2SO4 (16,19,22) were prepared as described. Aqueous solutions of GSH monoethyl ester were adjusted to pH 6.5-6.8 by cautious addition of 2 M NaOH just prior to injection; controls were given solutions containing equimolar levels of GSH, ethanol, and Na2SO4.…”

“…Mitochondrial and other cellular damage was prevented by simultaneous administration of GSH monoester but not by administration of GSH. GSH monoesters can enter cells effectively and are converted to GSH intracellularly (16)(17)(18)(19). In contrast, GSH is poorly transported into cells.…”

Glutathione regulates activation-dependent DNA synthesis in highly purified normal human T lymphocytes stimulated via the CD2 and CD3 antigens.

“…(ii) If the effect of BSO is mediated via decreased GSH synthesis, is the inhibition of proliferation a consequence of GSH depletion in T cells (mediators of antigen-specific immunity), or is it due to GSH deficiency, with consequent decrease of function, of the antigen-presenting (accessory) cells that generate the obligatory and costimulatory signals for T-cell activation? (iii) Can the inhibitory effect of BSO be prevented or reversed by correction of the GSH deficiency, for example by application of GSH monoester, which is well transported into cells and converted intracellularly to GSH (17)(18)(19)(20)(21)?…”