Peroxidase-positive endothelial cells in sinusoids of the mouse liver

The cytochemical localization of endogenous peroxidase activity in sinus lining cells of mouse liver has been investigated. Kupffer cells, as identified by their exclusive ability to phagocytize large (0.8 micron) latex particles, exhibited strong peroxidase activity in nuclear envelope and endoplasmic reticulum. In addition, weak to moderate peroxidase activity was found in 57% of all endothelial cells. The enzyme in endothelial cells was also localized in nuclear envelope and endoplasmic reticulum, with a negative reaction in the Golgi apparatus. These observations indicate that peroxidase staining, as a marker for identification of Kupffer cells in mouse liver, is only of limited value and should be used in conjunction with other methods (e.g., latex phagocytosis).