FIGURE 6.

Lowering pH of bath solution diminishes the inhibitory effect of Cu²⁺. Oocytes expressing WT αβγ hENaCs were clamped at −100 mV. A, a typical recording showing the effects of lowering bath solution pH from 7.4 (buffered with 5 mm MES and 5 mm MOPS) to 6.0 (buffered with 10 mm MES) on the base-line current and Cu²⁺ inhibition at 10 μm. The dark and light gray bars indicate the time periods in the presence of 10 μm amiloride in pH 6.0 and 7.4, respectively. There was no difference between the currents with amiloride at pH of 6.0 and 7.4. B, I_Cu/I at pH 7.4 and 6.0 (n = 7, p < 0.001). A control experiment at pH 7.4 was performed in the same way as in Fig. 2A. In experiments with both pH 6.0 and 7.4, 10 μm Cu²⁺ was applied for only 1 min to minimize potential complication from intracellular acidification, which inhibits ENaCs (47). The I_Cu/I obtained with 1 min of application of 10 μm Cu²⁺ at pH 7.4 was slightly greater than that with 3 min of application.