**5.1 ATP dependent sequestration of the GSH to the nucleus**

The role of ATP-dependent mechanisms in maintaining the nuclear/cytoplasmic GSH concentration in hepatocytes was demonstrated by Bellomo and co-workers (Bellomo et al., 1997). After 20 min of incubation with the uncoupler protonophore carbonyl cyanide mchlorophenylhydrazone (CCCP) the nuclear/cytoplasmic GSH gradient disappeared, but the total GSH content remain unchanged. This study was questioned by Briviba et al (Briviba et al., 1993) because of the use of monochlorobimane (BmCl). Despite its high specificity for glutathione this fluorochrome was found to be of no value in the study of cellular GSH distribution; once GSH-BmCl conjugate is formed it demonstrates an increased tendency of nuclear compartmentalization. Indeed, in our study using CMFDA, we have not found an ATP-dependent mechanism of nuclear GSH compartmentalization in 3T3 fibroblasts. Ho and Guenthner, 1997 using nuclear fractions concluded that GSH is taken up by the nucleus by passive diffusion and no evidence for an ATP-dependent mechanism for GSH concentration was observed.
