Initiation of check cell division by trypsin action at the cell surface.

Trypsin immobilised on polystyrene beads causes initiation of cell division which cannot be accounted for by trypsin released into the medium or into the cells. Also, initiation by soluble trypsin is inhibited by immobilised soybean trypsin inhibitor. These results demonstrate that trypsin can initiate proliferation at the cell surface.