All hexokinase isoenzymes coexist in rat hepatocytes

Abstract

The cellular distribution of hexokinase isoenzymes, N-acetylglucosaminase kinase and pyruvate kinases in rat liver was studied. Hepatocytes and non-parenchymal cells with high viability and almost no cross-contamination were obtained by perfusion in situ of the liver with collagenase, with the use of an enriched cell-culture medium in all steps of cell isolation. Separation of hexokinase isoenzymes was done by the DEAE-cellulose chromatography, and enzyme activities were measured by a specific radioassay. Cytosol from isolated hepatocytes contained high-affinity hexokinases A, B and C, in addition to hexokinase D. The last-mentioned represented about 95% of total glucose-phosphorylating activity. Only hexokinase A was found associated to the particulate fraction. Isolated non-parenchymal cells contained only hexokinases A, B and C. N-Acetylglucosaminase kinase was measured with a specific radioassay and was found as a single enzyme form in both hepatocytes and non-parenchymal cells, with higher activities in the former. Pyruvate kinase isoenzyme L was present in the hepatocytes and isoenzyme K only in the non-parenchymal liver cells, confirming that they are good cellular markers.