Effects of bradykinin on cell volume and intracellular pH in NIH 3T3 fibroblasts expressing the ras oncogene.

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/l) 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 of bradykinin is completely abolished in the presence of dimethylamiloride (100 mumol/l), which does not modify pHi in the absence of bradykinin. Similar to bradykinin, cell shrinkage by addition of 15 mmol/l 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 cells (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 of extracellular NaCl concentration by 15 mmol/l NaCl in +ras cells and by 7 mmol/l NaCl in -ras 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.