BCECF fluorescence has been applied to determine intracellular pH (pHi) in NIH 3T3 fibroblasts expressing the Ha-ras oncogene (+ras) and otherwise identical cells not expressing the oncogene (−ras). In +ras cells, pHi is significantly more alkaline (6.79 ± 0.03 n = 12) than in −ras cells (6.64 ± 0.02, n = 8). Bradykinin (100 nmol/1) leads to intracellular alkalinization in both +ras (to 6.96 ± 0.04, n = 12) and −ras cells (to 6.85 ± 0.02, n = 8). The effect or bradykinin is completely abolished in the presence of dimelhylamiloride (100μmol/1), which does not modify pHi in the absence or bradykinin. Similar to bradykinin, cell shrinkage by addition of 15 mmol/1 NaCl to the extracellular fluid leads to intracellular alkalinization (by 0.08 ± 0.01, n = 15). Cell volume is significantly greater in +ras cells (2.7 ± 0.4 pl, n = 15) than in −ras calls (2.2 ± 0.4 pl, n = 15), Bradykinin leads to cell shrinkage in both +ras cells (by 7 ± 1%, n = 17) and −ras cells (by 5 ± 1%, n = 15). The effect of bradykinin on cell volume can be reversed by the reduction or extracellular NaCl concentration by 15 mmol/1 NaCl in +ras cells and by 7 mmol/1 NaCl in −rus cells. This maneuver completely abolishes (in −ras cells) or blunts (in +ras cells) the alkalinizing effect of bradykinin. In conclusion, +ras cells are more alkaline than −ras cells. Bradykinin leads to further intracellular alkalinization by activation of the Na+/H+-exchanger, at least in part secondary to hormone-induced cell shrinkage.
