title: Dependence of energy transduction in intact skeletal muscles on the time in tension.
abstract: In intact single crayfish muscle fibers and frog semitendinosus muscles we have studied the tension response to sinusoidal length changes in the frequency range of 0.25-133 Hz. By this method we have resolved three processes in the interaction of myosin cross-bridges with actin in fully activated preparations. They are (A) a low-frequency phase advance, (B) a middle-frequency delay, and (C) a high-frequency advance. These processes can be used as probes to study the chemomechanical coupling of contractility. Process (B) represents net power output from the muscle preparation (oscillatory work). With maximal K or caffeine activation of crayfish muscle at 20 degrees C, it decreases to zero in the initial 45 s of maintained tension. Similar results were obtained with frog semitendinosus whole muscles. We interpret this decrease of (B) with time as a gradual decrease in actomyosin ATP-hydrolysis rate.
mesh_terms: D000205:Actomyosin / Q000378:metabolism*; D000251:Adenosine Triphosphatases / Q000378:metabolism; D000818:Animals; D001001:Anura; D003400:Astacoidea; D004735:Energy Transfer; D066298:In Vitro Techniques; D007700:Kinetics; D009119:Muscle Contraction; D009132:Muscles / Q000502:physiology*; D011894:Rana pipiens
chemical_list: D000205:Actomyosin; D000251:Adenosine Triphosphatases