Quantitative determination of the lateral diffusion coefficients of the hormone-receptor complexes of insulin and epidermal growth factor on the plasma membrane of cultured fibroblasts.

Fluorescent derivatives of insulin and epidermal growth factor bound to 3T3 mouse fibroblasts are mobile on the cell surface, with similar diffusion coefficients, D approximately (3--5) x 10(-10) cm2/sec at 23 degrees C. Increasing the temperature to 37 degrees C results in rapid receptor immobilization. The immobilization is attributed to aggregation of hormone-receptor complexes, their internalization, or a combination of both processes.