both the non-covalently cell surface-bound and the protease-nexin ( pn ) mediated-bound [ 125i ] -trypsin are internalized by the cells , but the [ 125i ] -trypsin x pn complexes contribute about 75 % of the total amount of [ 125i ] -trypsin internalized by the cells .
C0699040
cell surface
C0007634
cells