Localization of the thioredoxin system in normal rat kidney

Components of the thioredoxin system were localized in normal rat kidney us ing immunoperoxidase techniques at the light microscopic level and immunogo ld techniques at the ultrastructural level. Results from both methods were similar. Thioredoxin, thioredoxin reductases, and peroxiredoxins showed cel l-type-specific localization, with the same cell types (proximal and distal tubular epithelial, papillary collecting duct, and transitional epithelial cells) previously identified as having high amounts of antioxidant enzyme immunoreactive proteins and oxidative damage products also having high leve ls of proteins of the thioredoxin system. In addition, peroxiredoxins II an d IV were found in high levels in the cytoplasm of red blood cells, identif ied in kidney blood vessels. While thioredoxin and thioredoxin reductase 1 were found in all subcellular locations in kidney cells, thioredoxin reduct ase 2 was found predominantly in mitochondria. Thioredoxin reductase 1 was identified in rat plasma, suggesting it is a secreted protein. Peroxiredoxi ns often had specific subcellular locations, with peroxiredoxins III and V found in mitochondria and peroxiredoxin IV found in lysosomes. Our results emphasize the complex nature of the thioredoxin system, demonstrating uniqu e cell-type and organelle specificity. (C) 2001 Elsevier Science Inc.