Figure 1.

Comparison of Ca²⁺ 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 increasing intracellular free [Ca²⁺] indicated next to each current trace. The membrane potential was held at 0 mV. (B) Relationships between open probability and intracellular free [Ca²⁺] in control (●; n = 14) and mdx (○; n = 19) patches. In each patch, values of P_o were normalized to the value obtained in the presence of 2.5 mM intracellular Ca²⁺. The curves were fitted by using a Hill equation with n = 3.6 and K = 6.3 μM in control and n = 4.2 and K = 7.4 μM in mdx patches, respectively (see text).