Specific insulin-like growth factor I (IGF-I) receptors on a human erythroleukemia cell line (K-562cells) were identified and characterized.[125I] IGF-I specifically bound to K-562cells and the binding was displaced by unlabeled IGF-I in a dose dependent manner, and half maximal inhibition of the binding was observed at 7ng/ml IGF-I.[125I] IGF-I binding to the cells was displaced by multiplication stimulating activity (MSA) and by porcine insulin, with potencies that were10, and100times less than that of IGF-I, respectively. By an affinity labeling technique, IGF type I receptors were found to be present in the K-562cells. When the cells were differentiated by hemin (40μM), specific binding of [125I] IGF-I to the cells was decreased to 56.8±5.0% of that for undifferentiated cells. Furthermore, at physiological concentration of IGF-I stimulated thymidine incorporation into DNA and increased the number of cells.
These data demonstrate that K-562cells have specific receptors for IGF-I which may be functionally important for these cells, and that the IGF-I binding sites decrease with cell differentiation. This system might be useful in studying the interaction of IGF-I receptors.