Figure 3.

Comparison of NHE activity in the absence and presence of imetit, EIPA, thioperamide, and imetit plus thioperamide in SKNMC-H₃ cells. The mean control Na⁺-dependent pH_i recovery rate or NHE activity (pH_i units/min) is compared with rates measured in cells exposed to imetit (100 nM), EIPA (10 μM), thioperamide (300 nM), and thioperamide in combination with imetit. *, Significantly different (P < 0.0001) from control NHE activity. Values are means ± SEM, and n refers to the number of cells studied. Imetit, thioperamide, and EIPA were present in the superfusate from the NH₄Cl pulse to the end of the experiment. In the experiments with imetit and thioperamide in combination, thioperamide was first introduced in the NH₄Cl solution, and, 5 min later, imetit was added to the Na⁺-free solution, for an additional 5 min, before the reintroduction of Na⁺ into the superfusate.