Figure 1. Effects of exogenous PIP₂ (40 μm) on NCX1 currents in excised membrane patches.

A, outward exchange current in a mouse myocyte patch. Current is activated by applying Na⁺ to the cytoplasmic side (40 mm). Removal of cytoplasmic Ca²⁺ results in complete loss of current. After PIP₂ for 2 min, current does not inactivate and Ca²⁺ removal is without effect. B, outward exchange current in a patch from a BHK cell showing similarly complete ablation of exchanger inactivation reactions. Data points give means and standard errors of the mean for 7 equivalent experiments, normalized to the initial peak outward current. C, inward exchange current in an excised BHK patch. Current is activated repeatedly by solution with 100 or 3 μm free Ca²⁺, and application of PIP₂ is without effect. Data points give the means and standard errors of the mean for 5 equivalent experiments normalized to the initial peak inward current.