Stretch-induced activation of Ca2+-activated K+ channels in mouse skeletal muscle fibers

High-conductance Ca2+-activated K+ (K-Ca) channels were studied in mouse skeletal muscle fibers using the patch-clamp technique. In inside-out patches, application of negative pressure to the patch induced a dose-dependent and reversible activation of K-Ca channels. Stretch-induced increase in channel activity was found to be of the same magnitude in the presence and in the absence of Ca2+ in the pipette. The dose-response relationships between K-Ca channel activity and intracellular Ca2+ and between K-Ca channel activity and membrane potential revealed that voltage and Ca2+ sensitivity were not altered by membrane stretch. In cell-attached patches, in the presence of high external Ca2+ concentration, stretch-induced activation was also observed. We conclude that membrane stretch is a potential mode of regulation of skeletal muscle K-Ca channel activity and could be involved in the regulation of muscle excitability during contraction-relaxation cycles.