Extracellular acidosis delays cell death against glucose-oxygen deprivation in neuroblastoma x glioma hybrid cells.

Abstract

To determine whether extracellular acidosis delays cell death against glucose-oxygen deprivation and, if so, whether this result is due to inhibition of calcium (Ca2+) influx or preservation of cellular energy state. Randomized, controlled, prospective study. University research laboratory. Differentiated neuroblastoma x glioma NG108-15 cells. Experiment 1: cells were incubated for 8 hrs in N-(2-hydroxyethyl)piperazine-N'-2-ethanesulfonic acid-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 under glucose-oxygen deprivation after excluding extracellular calcium from 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-ethanesulfonic acid-buffered medium under glucose-oxygen deprivation at pH 7.4 or 6.2 and assayed for high-energy phosphates. 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 monophosphate were analyzed with high-performance liquid chromatography. Cell viability was significantly greater at pH 6.2 than at pH 7.4 in experiment 1. By excluding extracellular calcium, a significant difference in viability between pH 7.4 and 6.2 persisted in experiment 2. Energy charge and the concentration of adenosine triphosphate were significantly greater at pH 6.2 than at pH 7.4 in the intervals preceding manifestation of a differential effect of acidosis on cell viability in experiment 3. Extracellular acidosis at pH 6.2 delayed cell death against glucose-oxygen deprivation. This protective effect by extracellular acidosis may be due to preservation of the cellular energy state in NG108-15 cells, although this study does not exclude the possibility that in other cell types, inhibition of calcium influx may have an effect.