Ultrastructural demonstration of thioredoxin and thioredoxin reductase in rat hepatocytes

Electron microscopic immunocytochemistry, in conjunction with the immunogold technique, was used to demonstrate the ultrastructural localization of thioredoxin and thioredoxin reductase in rat liver hepatocytes. Gold particles representing thioredoxin and thioredoxin reductase antigenic sites were found throughout the cell, but particularly densely associated with the granular endoplasmic reticulum and the cisternae of the Golgi complex. Label was also distributed over the cytosol and in the chromatin of the nucleus. We conclude that thioredoxin and thioredoxin reductase are present in several different cellular compartments including the nucleus. In particular, the enrichment of thioredoxin and thioredoxin reductase to the endoplasmic reticulum is consistent with functions in protein processing, secretion and the formation of nascent protein disulfides.