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Variable Crossbridge Cycling-ATP Coupling Accounts for Cardiac Mechanoenergetics

  • Tad W. Taylor
  • Hiroyuki Suga
Part of the Advances in Experimental Medicine and Biology book series (AEMB, volume 332)

Abstract

Cardiac twitch contractions were simulated by Huxley’s sliding filament crossbridge muscle model. Huxley’s model was extended to include cardiac twitch contractions with a model structure having parallel and series elastic components with a crossbridge contractile element. The appropriate crossbridge energetics were added based on the crossbridge cycling rate and the energy of ATP hydrolysis. The force-length area (FLA) as a measure of the total mechanical energy was computed for both isometric and isotonic contractions in a manner similar to the pressure-volume area (PVA), (Suga, H. Physiol. Rev., 70, 247-277, 1990). Experimental studies have demonstrated that the pressure-volume area (PVA) correlates linearly with cardiac oxygen consumption and hence with the energy expenditure of a cardiac contraction. PVA correlates linearly with cardiac oxygen consumption, and since FLA is analogous to PVA, FLA should correlate with the ATP expended. Simulations comparing FLA with the crossbridge cycling ATP usage showed that at lower muscle fiber activation levels (shorter initial fiber lengths and lower preload levels) FLA decreased more rapidly than the number of muscle fiber crossbridge cycles. This could imply that one ATP can cause more than one crossbridge cycle at lower fiber activation levels as was proposed by Yanagida et al. (Nature, 316, 366-369, 1985). If the number of crossbridge cycles to ATP ratio is allowed to increase at lower activation levels, Huxley’s model agrees with the experimental findings on FLA and PVA.

Keywords

Fiber Length Isometric Contraction Cross Bridge Isotonic Contraction Total Mechanical Energy 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Springer Science+Business Media New York 1993

Authors and Affiliations

  • Tad W. Taylor
    • 1
  • Hiroyuki Suga
    • 2
  1. 1.National Cardiovascular Center Research InstituteSuita, OsakaJapan
  2. 2.The 2nd Department of PhysiologyOkayama University Medical SchoolOkayamaJapan

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