The gamma-glutamyl transferase activity and non-protein sulfhydryl compounds levels in rat kidney of different age groups

The present work was aimed to obtain information about age-dependent changes of γ-glutamyltransferase (GGT) activity and the levels of non-protein sulfhydryl com­pounds (NPSH) in rat kidneys. In addition, protein-bound cysteine (PB-Cys), sulfane sulfur compounds and reactive oxygen species (ROS) were estimated. The results indicate that the activity of GGT and NPSH levels in the kidneys are re­duced with age. At the same time, a significant increase in the level of protein-bound cysteine was observed. Simultaneously, the content of sulfane sulfur compounds was increased in the group of the oldest animals. These findings indicate that the capacity for extracellular glutathione degradation and, in consequence, the availability of cysteine for intracellular glutathione biosynthesis may be impaired. The increased PB-Cys level indicates potentiation of the thiolation reaction, i.e. development of pro­tein-mixed disulfides. These results reveal age dependent disturbances in the thiol-disulfide equilibrium in the kidneys which leads to an imbalance between pro- and antioxidatory processes.