Due to reports that tumor cells may have higher rates of H+ production, we became interested in the prospect of exploiting differences in intracellular pH (pHj) as a method to selectively target transformed cells. In this study, we used the pH-sensitive fluorescent dye BCECF to study pHj regulation in cultures of human glioblastomas compared to primary astrocytes as controls. Cultured cells were studied by fluorescent spectrophotometry while being constantly perfused with bicarbonate-free Ringer's solution at 37°C. Cells were subjected to an NH4CI "prepulse" to acidify the cell interior and permit a detailed study of pHj regulation. We found that the transformed cells displayed steady-state pHj values that were significantly higher (0.2 to 0.5 pH units) than the normal glial cells. This increased pHj must therefore reflect differences in either the fixed or dynamic buffering capabilities of the tumor cells. We determined that the fixed buffer capacity of the transformed cells was lower than the normal cells. Thus, given that the tumor cells have higher rates of H+ production, they would be even more dependent on dynamic buffering by the Na+/H+ exchanger than the normal cells. Recovery from an acid load was dependent on the presence of Na+ and was effectively blocked by amiloride, a known inhibitor of the Na+/H+ exchanger. Based upon these data, we propose that the glial tumor cells may have a higher intracellular pH set-point due to either differences in isoforms of the Na+/H+ exchanger or modifications of the signal transduction pathways. An understanding of the mechanisms involved may help us to develop an effective tumorselective therapy based upon differences in pHj.
|Original language||English (US)|
|State||Published - 1996|
ASJC Scopus subject areas
- Agricultural and Biological Sciences (miscellaneous)
- Biochemistry, Genetics and Molecular Biology(all)
- Cell Biology