Characterization of the renal epithelial cell line, PKE 5, using 31P- and 13C-NMR spectroscopy

In order to characterize intracellular pH regulation and cellular metabolism in PKE 5 cells, a mutant of the renal epithelial cell line LLC-PK1 supposed to lack Na+-H+ exchanger activity, 31P and 13C-NMR studies were conducted. The 31P studies on intact cell suspensions revealed that these cells have an ATP content and an ATP/ADP ratio similar to the parent cell line. Their intracellular pH, in the presence of 5 mM HCO3-, was 7.17 +/- 0.04 (n = 5) - identical to that of LLC-PK1 cells. After acid loading the cells with 15% CO2, the initial rate of realkalinization was 0.027 pH units/min (n = 6), 50% lower than in the parent cells. The recovery rate was not affected by the removal of extracellular sodium or by the addition of 1 mM amiloride. These results indicate that PKE 5 cells are devoid of Na+-H+ exchange activity, but are able to regulate their intracellular pH by amiloride-insensitive, sodium-independent mechanisms. Extracts prepared from PKE 5 cells incubated with [13C]lactate showed 13C spectra identical to those of the parent cell line. In particular, no synthesis of 13C-labeled D-glucose was observed.