Binding and biological actions of insulin-like growth factors on human arterial smooth muscle cells

Insulin-like growth factors (IGF) were isolated from human serum and compared with some biological actions of IGF supplied by Dr. J. Hapf, Zürich. Both factors were potent mitogens. They stimulated DNA-, RNA- and protein synthesis in cultivated human arterial smooth muscle cells. Furthermore, they enhanced the aminoacid transport. Our protein fraction (IGF Ulm) had a more potent biological activity than IGF (Zürich). Specific binding receptors for IGF (Zürich) on human arterial smooth muscle cells could be demonstrated. Specific binding of 125I-IGF (Zürich) was 10%. Half-maximal displacement was achieved by 250 ng/ml of unlabeled IGF (Zürich), by 1.2 micrograms/ml of IGF (Ulm), by 6.3 micrograms/ml of pro-insulin and by 17.8 micrograms/ml of insulin. In separate studies we could demonstrate that sera of normal adults, diabetic, acromegalic and hypophysectomized patients showed different growth-promoting activity in human arterial smooth muscle cells.