Retrospective Immunocytochemical Demonstration of Peroxisomal Enzymes in Human Liver Biopsies Processed Conventionally for Light and Electron Microscopy

Abstract

Indirect immunoperoxidase method was used to demonstrate by light microscopy peroxisomal catalase, acyl-CoA oxidase, enoyl-CoA hydratase, and 3-ketoacyl-CoA thiolase in human liver biopsies processed conventionally for light and electron microscopy. In both cases, controlled digestion with proteases (trypsin, pronase) was a prerequisite for a successful immunocytochemical reaction. Liver biopsies fixed with formalin and embedded in paraffin were found suitable for catalase immunostaining following deparaffinization, rehydration, and trypsin digestion. Samples fixed with glutaraldehyde and osmium tetroxide, and embedded in epoxy resin required resin removal with alkoxides, osmium removal with oxidants, and controlled proteolysis with trypsin or pronase. All the investigated peroxisomal enzymes could be detected by immunocytochemistry after such pretreatment of semithin sections. The employed procedures provide a possibility of carrying out retrospective studies on peroxisome content, number and distribution in tissue samples which so far have been regarded as suitable only for general morphological examination, and are therefore of potential value for investigation of human diseases associated with peroxisomal abnormalities.