Skeletal muscle calcium-activated neutral protease (calpain) with exercise.
The purpose of this study was to investigate whether exercise could induce calpain activation by altering the Ca2+ required for half-maximal activity (pCa50) and/or susceptibility of digestible muscle protein substrates. Rats (225 g) were assigned to control, exercise (25 m/min, 0% grade), and 24-h recovery groups. Exercise resulted in a generalized 48 +/- 18% loss of muscle glycogen and a twofold increase in plasma creatine kinase levels (P < or = 0.05). Exercise increased total caseinolysis of diethylaminoethyl Sepharose-prepared low (u) and high (m) Ca2+ calpain isoforms by 22 and 30%, respectively (P < or = 0.05). The pCa50 of u- and m-calpain with exercise increased from 5.98 +/- 0.12 to 6.20 +/- 0.15 (P > or = 0.05) and from 3.63 +/- 0.10 to 3.90 +/- 0.16 (P > or = 0.05), respectively. In vitro, calpain-mediated degradation/disappearance rates (i.e., percentage of protein degraded in 10 min) for control tropomyosin and alpha-actinin were 69 and 30% compared with 92 and 61% after exercise (P < or = 0.05). The results of this study confirm that level running increases total nonlysosomal Ca2+ specific protease activity, which may promote exercise-induced muscle damage or fatigue.
Belcastro
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Laboratory of Cell Physiology and Exercise, School of Human Kinetics, University of British Columbia, Vancouver, Canada.
D000818:Animals; D002154:Calpain / Q000378:metabolism*; D002364:Caseins / Q000378:metabolism; D003402:Creatine Kinase / Q000097:blood; D004789:Enzyme Activation / Q000502:physiology; D006003:Glycogen / Q000378:metabolism; D008297:Male; D009132:Muscles / Q000201:enzymology*; D009210:Myofibrils / Q000502:physiology / Q000648:ultrastructure; D005082:Physical Exertion / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012518:Sarcomeres / Q000502:physiology / Q000648:ultrastructure
D002364:Caseins; D006003:Glycogen; D003402:Creatine Kinase; D002154:Calpain