Transient changes in permeability in HeLa and L cells during detachment from a substrate.

The Na+ and K+ gradients of HeLa cells approach that of the medium during removal from a substrate with trypsin, but then recover during the next 15 min. The recovery is blocked by ouabain or the cold, but is unaffected by bumetanide. The effect is also obtained in cells which have no intercellular connexions, and in cells whose interior is made acid with CO2. Removal of cells with EDTA, pronase E and dispase has similar effects. It does not occur, or is greatly reduced, in cells already rounded up. Substances of molecular weight up to 5000 (e.g. inulin) also cross the cell membrane during this phase. We think that the effect is due to a transient increase in leakiness of the cell during rounding up, possibly due to the detachment of the 'feet' holding the cells onto the substrate. The transient increase in permeability of these cells may be a valuable method of introducing large molecules into them.