FIGURE 7.

Effect of CHP3 on affinity of NHE1 for intracellular protons. AP-1 cells stably expressing wild-type NHE1_HA alone or stably coexpressing NHE1_HA and CHP3_myc were cultured to confluence in 24-well plates. Initial rates of amiloride-inhibitable H⁺-activated ²²Na⁺ influx were measured at various intracellular H⁺ concentrations over the range of pH_i 5.4 to 7.4. The pH_i was adjusted by the K⁺-nigericin method, as described under “Experimental Procedures.” To facilitate comparison of the effects of CHP3, the data were normalized to their respective maximal rates of uptake. Values represent the mean ± S.E. of three experiments, each performed in triplicate. Error bars smaller than the symbol are absent.