Nonprotein thiols have been postulated as regulators of protein synthesis initiation in eukaryotes. 1 , 3 Almost 30 years ago, the classical studies of Zehavi-Willner et al. 4 suggested a correlation between glutathione (GSH) oxidation and inhibition of protein synthesis. Indeed, physiological levels of GSH appear to be essential for efficient protein synthesis in many cells. 5 Depletion of GSH and/or increase in intracellular levels of glutathione disulfide (GSSG) may lead to inhibition of protein synthesis, 5 , 6 Furthermore, by influencing nucleotide biosynthesis 7 and through reduction of ribonucleotides, 8 GSH metabolism may also play a role in the induction of DNA synthesis. It is known that intracellular GSH levels fluctuate during cell cycle 9 , 10 under different culture conditions, and that GSH may be important in the regulation of cellular proliferation. 11 However, it is unknown whether possible changes in DNA synthesis induced by GSH are accompanied by changes in protein synthesis.