Fig 2. Characterization of activity of wild type (WT) NHE1 and mutant (N266H) protein.

A, Example of Na⁺/H⁺ exchanger activity of stable cell lines containing wild type NHE1 and N266H NHE1 mutant protein. NHE1 protein activity was assayed in stably transfected AP-1 cells as described in the “Materials and Methods”. Results are typical of 5 independently made cell lines. For ease of viewing, only the recovery from acidosis is shown for the N266H protein. NH₄Cl, treatment with ammonium chloride. After NH₄Cl treatment there was a brief “Na Free” treatment to induce acidosis. NaCl, recovery from acidosis was in NaCl containing buffer. B, Summary of activity of WT and mutant ((N266H) NHE proteins in stably transfected cells. Activity was measured after ammonium chloride prepulse as described in the “Materials and Methods”. Results are change in intracellular pH/s. * indicates significantly different from wild type *P < 0.001, n>6. C, Summary of activity of WT and mutant (N266H) NHE proteins in transiently transfected cells. * indicates significantly different from wild type *P < 0.001, n = 8.