EXTRACELLULAR ACIDOSIS DELAYS CELL-DEATH AGAINST GLUCOSE-OXYGEN DEPRIVATION IN NEUROBLASTOMA X GLIOMA HYBRID-CELLS

Objective: To determine whether extracellular acidosis delays cell dea th against glucose-oxygen deprivation and, if so, whether this result is due to inhibition of calcium (Ca2+) influx or preservation of cellu lar energy state. Design: Randomized, controlled, prospective study. S etting: University research laboratory. Subjects: Differentiated neuro blastoma x glioma NG108-15 cells. Interventions: Experiment 1: cells w ere incubated for 8 hrs in N-(2-hydroxyethyl)piperazine-N'-2-ethane ac id buffered medium under glucose-oxygen deprivation at pH 7.4, 6.8, 6. 5, 6.2, 5.6, or 5.0, Experiment 2: cells were incubated for 8 hrs unde r glucose-oxygen deprivation after excluding extracellular calcium fro m culture medium at pH 7.4 or 6.2, Experiment 3: cells were incubated for 2, 4, 6, or 8 hrs in N-(2-hydroxyethyl)piperazine-N'-2 ethanesulfo nic acid-buffered medium under glucose-oxygen deprivation at pH 7.4 or 6.2 and assayed for high energy phosphates. Measurements and Main Res ults: Cell viability was measured with flow cytometry after the cells were stained with fluorescein diacetate and propidium iodide, Cellular adenosine triphosphate, adenosine diphosphate, and adenosine monophos phate were analyzed with high performance liquid chromatography, Cell viability was significantly greater at pH 6.2 than at pH 7.4 in experi ment 1, By excluding extracellular calcium, a significant difference i n viability between pH 7.4 and 6.2 persisted in experiment 2, Energy c harge and the concentration of adenosine triphosphate were significant ly greater at pH 6.2 than at pH 7.4 in the intervals preceding manifes tation of a differential effect of acidosis on cell viability in exper iment 3. Conclusions: Extracellular acidosis at pH 6.2 delayed cell de ath against glucose-oxygen deprivation. This protective effect by extr acellular acidosis may be due to preservation of the cellular energy s tate in NG108-15 cells, although this study does not exclude the possi bility that in other cell types, inhibition of calcium influx may have an effect.