Chapter

Muscle Biophysics

Volume 682 of the series Advances in Experimental Medicine and Biology pp 247-266

Date:

Crossbridge Mechanism(s) Examined by Temperature Perturbation Studies on Muscle

  • K. W. RanatungaAffiliated withMuscle Contraction Group, Department of Physiology and Pharmacology, School of Medical Sciences, University of Bristol Email author 
  • , M. E. Coupland

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Abstract

An overall view of the contractile process that has emerged from ­temperature-studies on active muscle is outlined. In isometric muscle, a small rapid temperature-jump (T-jump) enhances an early, pre-phosphate release, step in the acto-myosin (crossbridge) ATPase cycle and induces a characteristic rise in force indicating that crossbridge force generation is endothermic (force rises when heat is absorbed). Sigmoidal temperature dependence of steady force is largely due to the endothermic nature of force generation. During shortening, when muscle force is decreased, the T-jump force generation is enhanced; conversely, when a muscle is lengthening and its force increased, the T-jump force generation is inhibited. Taking T-jump force generation as a signature of the crossbridge – ATPase cycle, the results suggest that during lengthening the ATPase cycle is truncated before endothermic force generation, whereas during shortening this step and the ATPase cycle, are accelerated; this readily provides a molecular basis for the Fenn effect.

Keywords

Temperature perturbation Force generation Endothermic force Muscle force