CELL-GROWTH ON IMMOBILIZED CELL-GROWTH FACTOR .1. ACCELERATION OF THE GROWTH OF FIBROBLAST CELLS ON INSULIN-IMMOBILIZED POLYMER MATRIX IN CULTURE-MEDIUM WITHOUT SERUM

Culture of fibroblast cells in serum-free medium in the presence of insulin-immobilized films of poly(ethylene terephthalate) or poly(methyl methacrylate) accelerated the cell growth to several times that in the presence of free insulin molecules. The immobilization of insulin was useful also for elucidation of the mechanism of signal transmission through receptor molecules in the cell membrane. Free insulin molecules are known to be bound by receptors and the complex formed internalized and degraded in the cytoplasm, However, it is not clear what process is indispensable for transmission of the biological signals to the nucleus of the cell. The present investigation revealed that cell growth was enhanced by the addition of immobilized insulins which were not internalized. It appears that insulin-receptor binding is enough for transmission of the cell growth signal to the cell nucleus. The enhanced cell growth by the immobilized insulins compared with free insulin molecules is ascribable to suppression of the down-regulation which is a consequence of intracellular decomposition of the insulin-receptor complex.