RELATIONSHIP OF BINDING TO INTERNALIZATION OF I-125-INSULIN IN ISOLATED RAT HEPATOCYTES

By quantitative electron microscopic autoradiographic technique, we have previously shown that125I-insulin initially localizes to the plasma membrane of isolated rat hepatocytes and is subsequently internalized in a limited region of the peripheral cytoplasm. In the present study, we have shown that when cells are incubated at 20 °C, steady state binding is reached by 60 minutes and maintained up until 120 minutes of incubation while at 37 °C steady state binding is reached by 10 minutes and maintained for 30 minutes. Under both of these conditions, internalization of the labelled material occurs as a constant function of the binding. These data suggest that under normal conditions the binding of the ligand is an important rate limiting determinant of the internalization process. © 1979 Springer-Verlag.