Not all skeletal muscle fibers depend on the myoprotection of KATP channels during fatigue (1102.15)

Abstract

During fatigue, KATP channels are crucial in reducing action potential amplitude to eventually lower Ca2+ release by sarcoplasmic reticulum, which helps preserve ATP during a metabolic stress by decreasing Ca2+ ATPase and myosin ATPase activity. In the absence of KATP channel activity, skeletal muscle muscles suffer major contractile dysfunctions, which lead to faster fatigue rate because of fiber damage. In our studies at 37°C, we have observed a tremendous variability in the fatigue kinetics among mouse single FDB muscle fibers. Under control conditions, such variability is expected as fatigue resistance is in the order of type I>IIA>IIX>IIB (note IIB fibers are not present in FDB). However, we also observed a large variability in fatigue kinetics when KATP channels are completely blocked with 10 µM glibenclamide. Our results suggest that the importance of the KATP channel for myoprotection during fatigue is in the order of type IIX > IIA > I types, an order similar to the difference in KATP channel content between fiber types; i.e., the KATP channels are the most important in glycolytic fibers and the least important in oxidative fibers.Grant Funding Source: NSERC