The theory of sliding filament models for muscle contraction. I. The two-state model.
The mechanical and thermal properties of Huxley's 1957 sliding filament model for striated muscle contraction are reconsidered, with emphasis on general relationships between two-state models and muscle behaviour. New empirical forms for the rate functions f(x) and g(x) are proposed, which give an improved fit to experiments. A specific procedure, based on the shortening heat, for determining model parameters is described and applied to various choices of rate functions. The change in slope of the tension-velocity curve observed by Katz is shown to require at least one discontinuity in the binding rate f(x), and a general formula is given. The two-state model also gives a symmetric cusp in the ATP-rate vs velocity curve at v = 0. The theory is extended to time-varying situations and applied to transient responses following isometric activation by tetanus (including latency relaxation), and unloaded and after-loaded contractions. The early burst of heat production can also be fitted by assigning appropriate values to the heats of binding and dissociation.
Smith
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Department of Physics, Monash University, Clayton, Victoria, Australia.
Sicilia
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D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D001001:Anura; D006358:Hot Temperature; D008433:Mathematics; D008954:Models, Biological; D009119:Muscle Contraction; D012518:Sarcomeres / Q000648:ultrastructure; D013816:Thermodynamics
D000255:Adenosine Triphosphate