1. Parenchymal, Kupffer and biliary tract cells were isolated from normal rat liver by perfusion with collagenase solution.
2. The specific activities (munits of enzyme activity/mg of protein) of marker enzymes for the principal subcellular organelles were determined in the isolated cell homogenates and compared with whole liver homogenates.
3. The cells were disrupted and the extracts subjected to analytical subcellular fractionation by sucrose-density-gradient centrifugation. Lysosomal integrity was determined by assaying latent β-N-acetylglucosaminidase in the extracts.
4. Similar subcellular distributions were found for lysosomal, endoplasmic reticulum and plasma membrane marker enzymes in the whole liver and in parenchymal and biliary tract cells. In Kupffer cells, the proportion of these enzymes in the cytosol was significantly increased compared with the other fractions. In addition the equilibrium densities of the various organelles in these cells were lower than those from parenchymal cells.