The nature of insulin receptors in ascites hepatoma AH-66 were studied. The hepatoma plasma membranes were found to contain at least two types of insulin receptors with affinity constants of 9.0 × 109M^-1 and 2.8 × 109M^-1. Their affinity constants were almost equal to those in plasma membranes from normal rat liver. The capacity of the high affinity binding sites in AH-66 cells was larger by 50% as compared with that of normal liver. No differences were detected between AH-66 cells and normal livers in the inhibiting effect of concanavalin A on ¹²⁵I-insulin binbing. Furthermore, neither glucagon, ACTH, TSH, nor HGH inhibited ¹²⁵I-insulin binding to plasma membranes from AH-66 cells. Addition of 2mM N-ethylmaleimide to the assay system increased the affinity constant, binding capacity, and specific ¹²⁵I-insulin binding.
These results indicate that the plasma membrane of ascites hepatoma AH-66 has high and low affinity insulin receptors which are specific for insulin as that of the normal liver cell.