[Intracellular ph and the substrate dependence of Chinese hamster fibroblast proliferation]

Data have been presented on the effect of serum and of cell adhesion to a solid substrate on the intracellular pH (pHi) value in anchorage-dependent Chinese hamster fibroblasts. Proliferation of cells was observed in a pHi range from 7.0 to 7.5, which exceeded by 0.3-0.4 the pHi of quiescent cells. It was shown that attachment and spreading of cells in a bicarbonate-containing media without serum produced elevation of pHi from 6.7 to 7.1 but did not provide such an alkalization value for times greater than the lag period of cell growth. By the end of the first day after plating the pHi value of the spread cells in a serum-free medium reduced to 6.75, and the cells ceased to grow. The serum without cell attachment produced only a short-time (less than 1 h) pHi increase from 6.7 to 6.88, which was inadequate for cell growth. However, the serum produced a prolongation in cytoplasm alkalization characteristic of proliferation and caused by attachment of cells to a solid substrates. Evidence also was obtained for the absence of Na-independent HCO3-/Cl- exchange, the presence of a slow HCO3- transport into the cell and the key role of Na+/H+ exchange in pHi regulation. Addition to the bicarbonate-containing medium of amiloride, a blocker of Na+/H+ exchange, resulted in acidification of the cytoplasm to 6.5, and inhibited cell attachment and proliferation.