| Abstract: | To investigate the role of insulin-like growth factor II in the control of DNA synthesis in human fibroblasts, dose-response curves for insulin-like growth factor I and II stimulation of 3H]thymidine incorporation were compared in the absence and presence of alpha IR-3, a highly specific monoclonal antibody directed against the type I insulin-like growth factor receptor. Specific binding of 125I]insulin-like growth factor I to human fibroblast monolayer cultures was inhibited 60-70% in the presence of alpha IR-3. alpha IR-3 had no effect on 125I]insulin-like growth factor II binding to human fibroblasts. However, alpha IR-3 inhibited both insulin-like growth factor I and II stimulated 3H]thymidine incorporation. These data indicate that the type II insulin-like growth factor receptor does not function as a transducer of insulin-like growth factor II's mitogenic effect in human fibroblasts. |
