title: Energy liberation and chemical change in frog skeletal muscle during single isometric tetanic contractions.
abstract: Recent data obtained from Rana temporaria sartorius muscles during an isometric tetanus indicate that the time-course of phosphocreatine (PC) splitting cannot account for the total energy (heat + work) liberation (Gilbert et al. 1971. J. Physiol. (Lond.) 218:)63). As this conclusion is important to an understanding of the chemical energetics of contraction, similar experments were performed on unpoisoned, oxygenated Rana pipiens sartorius muscles. The muscles were tetanized (isometrically) at 0 degrees C for 0.6, 1, or 5 s; metabolism was rapidly arrested by freezing the muscles with a specially designed hammer apparatus, and the frozen muscles were chemically analyzed. Comparable myothermal measurments were made on frogs from the same batch. Results of these experiments indicate: (a) The energy liberation parallels the PC and ATP breakdown with a proportionality constant of 10.7 kcal/mol; (b) comparably designed experiments with sartorius muscles of R. temporaria revealed that the ratio of energy liberation to PC splitting was significantly greater than that observed in R. pipiens sartorius muscles; (c) there is no systematic difference between experiments in which metabolism was arrested by the hammer apparatus and others using a conventional immersion technique.
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism*; D000818:Animals; D001833:Body Temperature Regulation; D004734:Energy Metabolism; D006358:Hot Temperature; D066298:In Vitro Techniques; D008722:Methods; D009119:Muscle Contraction; D010100:Oxygen; D010725:Phosphocreatine / Q000378:metabolism*; D011894:Rana pipiens; D011896:Rana temporaria; D013997:Time Factors
chemical_list: D010725:Phosphocreatine; D000255:Adenosine Triphosphate; D010100:Oxygen