[Thermal effect of interaction of ATP with flaccid and contracted glycerinized fibers].

Heat accompanying the interaction between relaxed and contracted glycerinized fiber bundles of the striated muscles of rats and ATP was measured. Investigation of the interaction concerned both relaxed and preliminarily contracted bundles. As apparent from the thermokinetic curves, the interaction of ATP with the noncontracted bundles yields a peak of the thermal potency which coincides in time with the contraction process; no such effect was produced in case of preliminarily contracted fibers. The authors conclude that a direct interrelationship exists between the rate of ATPase activity and the conformation of actomyosin system.