Insulin receptors in cultured human keratinocytes

Insulin binding to receptors was studied for the first time in cultured normal epidermal human keratinocytes. Binding was measured at 16 degrees C in steady-state conditions using 125I-labelled iodohormone and varying concentrations of unlabelled hormone. Insulin binding was compatible with either a two-site model--a high affinity site (about 6000 sites per cell) and a low affinity site (about 88,000 sites per cell) site--or one class of binding site with negatively co-operative interactions, or both these models may operate. Insulin receptors (IR) have been extensively studied in various biological systems, but not in epidermal cells. However, insulin resistance with defects in IR may be associated with cutaneous abnormalities (acanthosis nigricans). This led us to study insulin binding on normal human keratinocytes in culture.