Effects of an oxidizing agent (hydrogen peroxide) on the glutathione system in epidermal cells of Allium cepa L. investigated by histochemical staining

The glutathione system in epidermal cells of Allium cepa L. was measured by a quantitative image analysis method, using histochemical staining by monr ochlorobimane. Blockage of thiol groups with N-ethylmaleimide decreased flu orescence to a small rest fluorescence of maximum 5%. Pre-treatment with di thiothreitol increased fluorescence yield in all cells compared to the mono chlorobimane treatment alone. These results correspond to the blockage or t he reduction of the total pool of glutathione in the cells. After treatment with N-ethylmaleimide and subsequent incubation with dithiothreitol follow ed by labelling with bimane a low fluorescence yield was observed which cor respond to the proportion of GSSG. Specimens that were incubated in H2O2 pr ior to the treatments described above exhibited a decrease in total glutath ione and in reduced glutathione and an increase in the proportion of GSSG c ompared to the control.