Myofibril ATPase activity of cardiac and skeletal muscle of exhaustively exercised rats |
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| Authors: | A N Belcastro R Turcotte M Rossiter D Secord P E Maybank |
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| Affiliation: | 1. Department of Pharmacy, Uppsala University, 751 23 Uppsala, Sweden;2. Biochemical Proteomics Group, Department of Proteomics and Signal Transduction, Max Planck Institute of Biochemistry, 82152 Martinsried, Germany;3. Uppsala University Drug Optimization and Pharmaceutical Profiling Platform, Uppsala University, 751 23 Uppsala, Sweden;4. Science for Life Laboratory Drug Discovery and Development Platform, Uppsala University, 751 23 Uppsala, Sweden;1. Laboratory of Biocrystallography and Computational Molecular Biology, Department of Physics, Periyar University, Salem, 636 011, India;2. Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore, 560 012, India;1. Department of Biological Regulation, Weizmann Institute of Science, Rehovot 76100, Israel;2. Department of Veterinary Resources, Weizmann Institute of Science, Rehovot 76100, Israel;3. Department of Chemical Research Support, Weizmann Institute of Science, Rehovot 76100, Israel;4. Hematology Institute, Kaplan Medical Center, Rehovot 76100, Israel;5. Cardiovascular, Metabolic, and Endocrine Diseases (CVMED) Research Unit, Pfizer Inc., 610 Main Street, Cambridge, MA 02139, USA |
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| Abstract: | The activation characteristics of Mg-ATP and Ca2+ on cardiac and skeletal muscle myofibril ATPase activity were studied in rats following a run to exhaustion. In addition, the effect of varying ionic strength was determined on skeletal muscle from exhausted animals. The exhausted group (E) ran at a speed of 25 m min-1 with an 8% incline. Myofibril ATPase activities for control (C) and E were determined with 1, 3 and 5 mM Mg-ATP and 1 and 10 microM Ca2+ at pH 7.0 and 30 degrees C. For control skeletal muscle, at 1 and 10 microM Ca2+, there was an increase in ATPase activity from 1 to 5 mM Mg-ATP (P less than 0.05). For E animals the myofibril ATPase activities at 10 microM Ca2+ and all Mg-ATP concentrations were similar to C (P greater than 0.05). At 1.0 microM Ca2+ and all Mg-ATP concentrations were similar to C (P greater than 0.05). At 1.0 microM Ca2+ the activities at 3 and 5 mM Mg-ATP were greater for the E animals (P less than 0.05). Increasing KCl concentrations resulted in greater inhibition for E animals. With cardiac muscle, the myofibril ATPase activities at 1.0 microM free Ca2+ were lower for E at all Mg-ATP levels (P less than 0.05). In contrast, at 10 microM Ca2+, the E group exhibited an elevated myofibril ATPase activity. The results indicate that Mg-ATP and Ca2+ activation of cardiac and skeletal muscle myofibril ATPase is altered with exhaustive exercise. |
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