MECHANISM OF CELLULAR SWELLING-INDUCED BY EXTRACELLULAR LACTIC-ACIDOSIS IN NEUROBLASTOMA-GLIOMA HYBRID (NG108-15) CELLS

The mechanism of cellular swelling induced by extracellular lactic aci dosis and the effect of diuretics were studied using neuroblastoma-gli oma hybrid (NG108-15) cells. The cells were incubated in one of three lactate concentrations (0, 15, or 30 mM), each of which was randomized to one of three pH groups (7.4, 6.2, or 5.0). Analysis of the swellin g was measured using a Coulter counter technique. Cellular swelling wa s most prominent at pH 6.2 at all lactate levels. Cellular swelling wa s noted to be pH dependent but not lactate dependent. The addition of 1 mM amiloride completely blocked cellular swelling, suggesting that t he main mechanism of neuronal cellular swelling induced by extracellul ar lactic acidosis was the activation of Na+/H+ exchange. Second, thre e dissimilar diuretic drugs were used for cellular swelling: amiloride (Na+/H+ exchange inhibitor), mannitol (osmotic diuretic), and bumetan ide (loop diuretic). Amiloride and mannitol were found effective in re ducing the lactic acidosis-induced cellular swelling. Furthermore, the combination of these drugs had additive effects. However, bumetanide was not effective. The results indicate that the direct inhibition of Na+/H+ exchange and/or removal of water from the cell by mannitol was effective against cellular swelling induced by the activation of Na+/H + exchange in NG108-15 cells.