FIGURE 6.

The patch capacitance and presumably the gross mechanics of the membrane are not altered at pH 6.5. We measured the conductance (black) and capacitance (gray) in cell-attached mode at pH 6.5 (A) and compared it with the response at pH 7.3 (B). With suction pulses (light gray), the PIEZO1-driven conductance increased at the first pulse, followed by a decrease in peak conductance with subsequent pulses. The time dependence of the capacitance change with pressure was fit to a first-order exponential to provide fiducial parameters. The rise time constants (τ) for both pH solutions were similar, indicating that pH does not appear to significantly modify the basic mechanics of the patch. Thus, the pH effect on channel kinetics is probably an effect upon the channel itself and not adaptation of the local forces produced by viscoelastic relaxation of the membrane (membrane voltage of −80 mV, suction of −30 mm Hg).