Temperature and the energy cost of oscillatory work in teleost fast muscle fibres.
Bundles of 20-30 fast muscle fibres were isolated from the abdominal myotomes of the short-horned sculpin (Myoxocephalus scorpius L.). The energy cost of contraction was measured during oscillatory work at 4 degrees C and 15 degrees C following treatment with iodoacetate and nitrogen gas to block glycolysis and aerobic metabolism. Isolated fibres were subjected to sinusoidal length changes about in situ resting length and stimulated at a selected phase in the strain cycle. Preliminary experiments with untreated preparations established the strain amplitude and stimulation parameters required to maximize work output over a range of cycle frequencies at 4 degrees C and 15 degrees C. Following oscillatory work, treated preparations were rapidly frozen, freeze-dried and the concentrations of phosphocreatine (PCr), creatine, adenosine 5'-triphosphate (ATP), adenosine 5'-di- and mono-phosphate and inosine 5-monophosphate measured by high performance liquid chromatography. The concentration of PCr declined in proportion to the total work done for up to 64 cycles without a significant change in ATP. Maximum power output was produced at a cycle frequency of 5 Hz at 4 degrees C (14-18 W/kg) and 17 Hz at 15 degrees C (23-27 W/kg). The rate of utilization of PCr per cycle was independent of temperature. However, since work per cycle was higher at 4 degrees C (2.7-3.7 mJ/g wet weight) than 15 degrees C (1.2-1.6 mJ/g wet weight), the energetic cost of contraction decreased with increasing temperature.
Johnson
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Gatty Marine Laboratory, Department of Biology and Preclinical Medicine, University of St. Andrews, Fife, Scotland, UK.
Johnston
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Moon
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D000255:Adenosine Triphosphate / Q000378:metabolism; D000704:Analysis of Variance; D000818:Animals; D004734:Energy Metabolism; D005399:Fishes; D009119:Muscle Contraction; D009991:Oscillometry; D010725:Phosphocreatine / Q000378:metabolism; D013696:Temperature
D010725:Phosphocreatine; D000255:Adenosine Triphosphate