title: Energetics of relaxation in frog muscle.
abstract: 1. Changes in the levels of phosphocreatine (PCr) and ATP during relaxation after tetanic contraction have been observed and compared with the heat + work production during the same period.2. The results were the same using 2 sec or 15 sec tetani and using 15 or 30 Hz stimulation.3. During relaxation the mean chemical change (of ATP + PCr) was -0.105 +/- 0.078 mumol/g muscle (n = 53). This change is less than would be required to explain the heat + work produced.4. The PCr split during both 2 sec and 15 sec tetani (up to the last stimulus) was less than would be required to explain the heat + work produced. This confirms previous experiments.5. It is concluded that the discrepancy between chemical change and heat + work production does not diminish during relaxation but actually increases.
mesh_terms: D000255:Adenosine Triphosphate / Q000032:analysis / Q000378:metabolism*; D000818:Animals; D001001:Anura; D003401:Creatine; D004558:Electric Stimulation; D004734:Energy Metabolism; D066298:In Vitro Techniques; D009119:Muscle Contraction; D009132:Muscles / Q000032:analysis / Q000378:metabolism*; D010725:Phosphocreatine / Q000032:analysis / Q000378:metabolism*; D011896:Rana temporaria
chemical_list: D010725:Phosphocreatine; D000255:Adenosine Triphosphate; D003401:Creatine