Alteration of glutathione level in human melanoma cells: effect of N-acetyl-L-cysteine and its analogues

The effects of N-acetyl-L-cysteine (L-NAC), N,N-diacetyl-L-cystine (oxidized form of L-NAC) and N-acetyl-D-cysteine on the intracellular glutathione (GSH) level and their toxicity were investigated in the human melanoma cell culture IGR1. L-NAC applied in 3 mM concentration for 24 hr decreased; when applied for 48 hr it did not alter the intracellular GSH level. Treatment with 1 mM L-NAC for 24 hr had no effect on cellular glutathione, whereas the same concentration applied for 48 hr resulted in an increase in the level of GSH. Both concentrations also induced cell injury as determined by protein assay and trypan blue staining. N,N-diacetyl-L-cystine (0.5 and 1.5 mM, 24 hr) induced a decrease in cellular glutathione content without any apparent cell toxicity. D-NAC (1 and 3 mM, 24 hr) did not influence the GSH level of the melanoma cells; however, it had toxic effects resulting in cell loss.