THE CONTROL OF ENERGY RELEASE IN EXTRACTED MUSCLE FIBERS

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Abstract
Tension and liberation of V were detd. simultaneously during the contraction cycle in glycerol-extracted muscle fibers (m.psoas of rabbit) suspended in solns. containing ATP, KC1, and MgCl2. During a strong contraction P liberation is about 5 times greater than in the relaxed state. Contractions can be produced in relaxed fibers by adding small amts. of CaCl2 or by removing MgCl2. While extracted muscle fibers relaease less energy during contraction, they maintain tension more economically than normal fibers, resembling in this respect smooth muscle. Aged muscle fibers do not relax, are activated by Mg, but not by Ca. In the relaxed state, energy release is greater than in normal muscle. Addition of 0.2 - 0.4 x 104 [image] pyrophosphate lowers this value about 40%.

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