INTRACELLULAR PH AND ANCHORAGE DEPENDENCE OF PROLIFERATION OF CHINESE-HAMSTER FIBROBLASTS

Data have been presented on the effect of serum and of cell adhesion to a solid substrate on the intracellular pH (pH(i)) value in anchorage-dependent Chinese hamster fibroblasts. Proliferation of cells was observed in a pH(i) range from 7.0 to 7.5, which exceeded by 0.3-0.4 the pH(i) of quiescent cells. It was shown that attachment and spreading of cells in a bicarbonate-containing media without serum produced elevation of pH(i) 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 pH(i) 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) pH(i) 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 pH(i) 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.