CYTOCHEMICAL-LOCALIZATION OF CATALASE AND PEROXIDASE IN SINUSOIDAL CELLS OF RAT-LIVER

Abstract

The cytochemical localization of catalase and peroxidase in various sinusoidal cells of rat liver, i.e., in Kupffer cells, endothelial cells and fat-storing cells was investigated. The alkaline 3,3''-diaminobenzidine technique reveals distinct catalase-positive particles in all 3 cell types. The particles are round to oval-shaped, measuring 0.1-0.3 .mu.m in diameter. The diaminobenzidine reaction product is distributed uniformly over their matrix, often obscuring the distinct limiting membrane. In fat-storing cells the particles appear in close proximity of lipid droplets. No evidence of fusion of the limiting membrane of the particles with that of phagolysosomes containing latex particles was observed. The catalase-positive particles appeared often in close proximity of endoplasmic reticulum, but by examining consecutive serial sections there was no evidence of direct continuity between the 2 organelles. In addition to catalase there is an endogenous peroxidase in the endoplasmic reticulum and nuclear envelope of Kupffer cells. Whereas peroxidase is sensitive to aldehyde fixation and has its optimal pH in the neutral range, the staining for catalase requires prior fixation with glutaraldehyde and is optimal at pH 10.5. By using proper fixation and incubation conditions the 2 enzymes were visualized selectively, and they occupy 2 distinct intracellular compartments within the Kupffer cells: the catalase in the matrix of particles and the peroxidase in the endoplasmic reticulum. The possible functional role of catalase in various sinusoidal cells is briefly discussed.