Intracellular free Mg2+ with pH changes in cultured epithelial cells

Intracellular pH (pHi) alters cytosolic concentrations of electrolytes, including Ca2+ and Na+. The present studies determined the effect of pHi on intracellular free Mg2+ activity in two epithelial cell lines: one possessing absorptive and secretory functions (Caco-2 intestinal cells) and the second, an absorptive kidney cell line derived from the opossum kidney (OK).pHi and spatial H+ distribution were assessed by 2',7'-bis(carboxyethyl)-5(6')-carboxyfluorescein after an NH4+ pulse to provide rapid changes in pHi. [Mg2+]i, [Ca2+]i, and [Na+]i were measured by fluorescence techniques. [Mg2+]i and spatial Mg2+ distribution within single cells were not changed with rapid alkalinization and acidification procedures in both intestinal and renal cell lines. Alkalinization results in significant increases in [Ca2+]i and [Na+]i that return to basal levels after acidification in both Caco-2 and OK cell lines. These studies indicate that [Mg2+]i is not altered with changes in pHi and suggest that [Mg2+]i is maintained by means not related to pHi in these epithelial cells.