The internalisation of [125I] insulin by isolated rat hepatocytes

This work was undertaken to examine the relationship between the binding, internalisation and degradation of insulin by isolated rat hepatocytes. Internalisation of hormone reached a maximum after 5-7 minutes at 37 degrees C; at an insulin concentration of 0.1 nM, 25% of the specifically bound hormone was internalised. Internalisation and the degradation of internalised insulin were inhibited by the intralysosomal protease inhibitors chloroquine and methylamine but not by the thiol oxidant diamide. It is concluded that internalisation of insulin by rat hepatocytes is not a necessary step in the degradation of the hormone molecule.