Effects of age on rat liver enzymes. A study using isolated hepatocytes, endothelial and Kupffer cells.

Hepatocytes, endothelial and Kupffer cells were isolated from young adult (3 month) and old (24 month) rat livers and the activities of some plasma membrane, endoplasmic reticulum, mitochondrial, lysosomal and soluble enzymes compared using biochemical and electron microscope cytochemical techniques. Age-associated changes included: a decrease in glucose-6-phosphatase activity both in hepatocytes and sinus lining cells; and increase in alkaline phosphatase in endothelial cells but a decrease in hepatocytes; reduced basal and glucagon-induced adenyl cyclase in hepatocytes and endothelial cells and an increase in the number of hepatocytes with gamma-glutamyl transferase reaction. Cytochemistry showed that heterogeneity may also be characteristic of senescence particularly with regard to hepatocyte glucose-6-phosphatase which was absent in some cells, low in many cells but high in some and gamma-glutamyl transferase which was normally lacking from hepatocytes but localised as large deposits of reaction product on the plasma membranes of occasional cells isolated from old donors.