Figure 5.
Low pH inhibits use-dependent inactivation in NaV1.5+β1. pH modulation of use-dependent inactivation was measured at pH 7.4 (squares) and pH 6.0 (circles). (A) The data were normalized to the first pulse, plotted as a function of time, and fitted with a double exponential. Lines depict respective fits with a double exponential equation, and the pulse protocol used is displayed in the inset. (B) Values derived from double exponential fits at pH 7.4 (open) and pH 6.0 (filled). The fast (τf) and slow (τs) time constants of use-dependent inactivation were significantly increased at pH 6.0 (gray) compared with pH 7.4 (white). (C) Change in the asymptote of use-dependent inactivation plotted as a function of pH. Values obtained at pH 7.4 were significantly different from those obtained at pH 6.4 and 6.0. All data points are mean ± SE; ∗ indicates statistical significance at p < 0.05.