IMMUNOCYTOCHEMICAL STUDY OF BINDING AND INTERNALIZATION OF CARRIER-FREE CU, ZN SUPEROXIDE-DISMUTASE BY CULTURED RAT HEPATOCYTES

Internalization of superoxide dismutase-gold complex by isolated liver cells has been shown to occur via receptor-mediated endocytosis. As c olloidal gold may act as a carrier in this process, carrier-free human Cu, Zn superoxide dismutase was incubated with cultured rat hepatocyt es. Light and electron microscopy immunocytochemistry revealed the bin ding and internalization of free native human Cu, Zn superoxide dismut ase (hSOD) by cultured rat hepatocytes. Immunocytochemical demonstrati on of binding to the cell surface (hepatocytes were incubated with hSO D for 15 min. at 4 degrees C) and internalization (hepatocytes were in cubated with hSOD for 15, 30 and 60 min. at 37 degrees C) of the carri er-free superoxide dismutase was achieved by using a monoclonal antibo dy selectively reacting with the human protein. The results obtained i ndicate that carrier-free superoxide dismutase is bound and internaliz ed by rat hepatocytes in primary cultures and that the enzyme can ente r the cells via a receptor-mediated endocytosis pathway. We followed t he binding and the internalization process of hSOD thus validating the use of the native enzyme in the therapy of free radical-related disea ses.