Light microscopic immunocytochemical demonstration of peroxisomal enzymes in epon sections

A procedure is described for light microscopic immunocytochemical localization of catalase and three enzymes of peroxisomal lipid beta-oxidation: acyl-CoA oxidase, enoyl-CoA hydratase and 3-ketoacyl-CoA thiolase in semi-thin sections of rat liver processed for routine electron microscopy. Satisfactory immunostaining required the removal of the epoxy resin with sodium ethoxide, controlled digestion of deplasticized sections with proteases and, in case of osmiumfixed tissue, bleaching with oxidants. Resin removal was essential for successful immunostaining, and protease treatment enhanced markedly the intensity of the reaction. This study shows that tissues processed for conventional ultrastructural studies can be used for postembedding immunocytochemical demonstration of various peroxisomal enzymes.