Figure 2.

Comparison of voltage sensitivity of K_Ca channels in inside-out patches from control and mdx muscle fibers. (A) Segments of single K_Ca channel currents recorded in the presence of 4.4 μM intracellular free [Ca²⁺] at different membrane potentials indicated next to each current trace. (B) Relationships between open probability and membrane potential in control (●) and mdx (○) patches. In each patch, values of P_o were normalized to the value obtained at 0 mV in the presence of 2.5 mM intracellular Ca²⁺. The curves were fitted with a Boltzmann equation with V_1/2 = 6.8 mV and k = 15.6 mV in control and V_1/2 = 10.4 mV and k = 12.1 mV in mdx patches, respectively (see text). (C) Current-voltage relationships of K_Ca channels in control (●; n = 14) and mdx(○; n = 17) patches. The curve was drawn by eye.