Correlations of ATP content with mechanical properties of metabolically inhibited muscle

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Abstract
This investigation was designed to provie quantitative information on the relationships between the adenosine triphosphate (ATP) content of a living muscle and the ability of the muscle to develop tension on stimulation and the extent to which the unstimulated muscle maintains a normal relaxed state. Frog sartorius muscles with varying ATP contents were obtained by metabolically inhibiting the muscle with l-fluoro-2,4-dinitrobenzene and then depleting the ATP stores through contractile activity. The isometric tetanus tension output of inhibited muscles was found to be directly proportional to the log ATP content. The tension produced in an unstimulated muscle by a 1 -mm quick stretch was used as an index of the degree of association of the contractile filaments. When the ATP content was between 1.5 and 0.25 [mu]mole/g muscle wet wt, quick-stretch tension was inversely proportional to the log ATP content. The mechanical properties of ATP-depleted muscles and the development of rigor may be interpreted as a result of the interaction between ATP-dependent relaxation and contraction mechanisms.