Localization and function of ATP-sensitive potassium channels in human skeletal muscle

The present study investigated the localization of ATP-sensitive K+ (K-ATP) channels in human skeletal muscle and the functional importance of these channels for human muscle K+ distribution at rest and during muscle activity. Membrane fractionation based on the giant vesicle technique or the sucrose-gradient technique in combination with Western blotting demonstrated that the K-ATP channels are mainly located in the sarcolemma. This localization was confirmed by immunohistochemical measurements. With the microdialysis technique, it was demonstrated that local application of the K-ATP channel inhibitor glibenclamide reduced (P < 0.05) interstitial K+ at rest from ∼4.5 to 4.0 mM, whereas the concentration in the control leg remained constant. Glibenclamide had no effect on the interstitial K+ accumulation during knee-extensor exercise at a power output of 60 W. In contrast to in vitro conditions, the present study demonstrated that under in vivo conditions the K-ATP channels are active at rest and contribute to the accumulation of interstitial K+.