Cytochemical localization of catalase and peroxidase in sinusoidal cells of rat liver.

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 has been investigated. The alkaline 3,3'-diaminobenzidine technique reveals distinct "catalase-positive particles" in all three cell types. The particles are round to oval-shaped, measuring 0.1 to 0.3 mum. 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 we could not find any convincing evidence of direct continuity between the two 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 isoptimal at pH 10.5. By using proper fixation and incubation conditions the two enzymes have been visualized selectively, and it is demonstrated that they occupy two 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.