PROTECTIVE EFFECTS OF GLUTATHIONE ISOPROPYL ESTER ON THE SENSITIVITY OF CULTURED-CELLS TO UVB IRRADIATION

The effect of glutathione (GSH) isopropyl ester on cellular sensitivit y to UVB irradiation was investigated in HeLaS3 cells. Pretreatment wi th 0.1-0.5 mM GSH isopropyl ester for 4 h significantly inhibited the decrease of thymidine (TdR) incorporation caused by UVB irradiation at a dose of 500 J/m(2), whereas pretreatment with a high dose (1 mM) ha d no effect. The colony formation ability of the pretreated cells (0.3 mM) was significantly better than that of cells that received irradia tion only. When the cells were treated with GSH isopropyl ester, their intracellular GSH level increased dose-dependently over a 4 h period, suggesting that GSH isopropyl ester was transported into the cells an d there converted to GSH. Within 2 min of exposure, the intracellular GSH level depleted rapidly to about 75% of that in non-irradiated norm al cells. In contrast, the GSH level in cells pretreated with 0.3 mM G SH isopropyl ester was maintained at the same level as that in normal cells, indicating that the maintenance of intracellular GSH level is d ue to converted GSH from GSH isopropyl ester. These results clearly sh ow that intracellular GSH is involved in cell protection against photo damage, and that GSH isopropyl ester is a useful antioxidant for prote ction against photooxidative injury.