Phenotypic differences between the actomyosin ATPase of the three fiber types of mammalian skeletal muscle

We present our finding that the ATPase of the high-activity fibers is labile in acid and the ATPase of the low-activity fibers is labile in alkali

Frederick J. Samaha


Key concepts

Scholarcy highlights

  • It is known that most mammalian hind limb muscles are composed of three types of muscle fibers when formalin-fixed tissue sections are stained for actomyosin ATPase activity
  • The C fibers are high, the B fibers low, and the A fibers intermediate in enzyme activity
  • The ATPase of the intermediate-activity fibers is intermediate with respect to pH lability; its ATPase is more resistant to acid than is that of the C fibers and is more resistant to alkali than is that of the B fibers
  • These muscle fibers are phenotypically different with respect to their actomyosin ATPase. The implications of these differences are noteworthy with reference to typing of muscle fibers in disease, neurotrophic influence on muscle fiber types, and genetic constitution of the skeletal muscle fiber

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