It was shown that activation of the Na+/H+ antiporter resulting in an increase of intracellular pH (pHi) by 0.2–0.3 is a necessary stage of cell stimulation by soluble growth factors. Solid substrate can also be formally regarded as a growth factor since adhesion stimulates proliferation of various cell types. In the present study we have found that the attachment of mouse embryo fibroblasts to solid substrate is followed by an increase of pHi by approx. 0.3 units. pH shift occurs after the cell attaches to the substrate and is obligatory for cell spreading. The evidence for Na+/H+ antiporter involvement in the increase of pHi in substrate-attached cells is presented. It is suggested that signals for cell proliferation by chemical (soluble ligands) and physical (solid substrate) growth factors are transmitted similarly.
