Striated muscle calcium-stimulated cysteine protease (calpain-like) activity promotes myeloperoxidase activity with exercise.
An inflammatory response triggered by neutrophil accumulation into muscle tissue is thought to occur with exercise-induced muscle damage. To investigate the relationship between Ca2+-stimulated proteolysis (calpain-like activity) and neutrophil accumulation [myeloperoxidase (MPO) activity], cardiac and plantaris muscles from rats (n = 10) completing 1 h exercise (25 m/min) were investigated. Exercise promoted increases (P<0.05) in both calpain-like and MPO activities; ranging from 2.79 to 58.9 U/g wet weight (ww) and 0.03 to 4.88 U/g ww respectively. Pearson's correlational analysis (r) on calpain-like and MPO activities for cardiac and plantaris muscle data were 0.97 (P<0.001) and 0.68 (P<0.05) respectively, with a combined r of 0.83 (P<0.001) for both muscles across all conditions. To investigate further the extent to which calpain-like activity may promote neutrophil accumulation, another exercise group (n = 5) was pre-injected with the cysteine protease inhibitor, E64c, 1 h before exercise. Administration of E64c lowered calpain-like and MPO activities by 66% and 56% respectively (average from both muscles). From these results it is concluded that a relationship exists between Ca2+-stimulated proteolysis and neutrophil accumulation into striated muscle with exercise, and that the calpain system is involved in localizing the neutrophilic response with exercise.
Raj
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DA
School of Rehabilitation Sciences, University of British Columbia, Vancouver, B.C., V6T 2B5, Canada.
Booker
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Belcastro
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D000818:Animals; D002154:Calpain / Q000378:metabolism*; D003402:Creatine Kinase / Q000097:blood; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D007930:Leucine / Q000031:analogs & derivatives / Q000494:pharmacology; D008297:Male; D018482:Muscle, Skeletal / Q000201:enzymology*; D009206:Myocardium / Q000201:enzymology; D009504:Neutrophils / Q000201:enzymology / Q000502:physiology; D009195:Peroxidase / Q000378:metabolism*; D005082:Physical Exertion / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar
D015853:Cysteine Proteinase Inhibitors; C032425:N-(N-(3-carboxyoxirane-2-carbonyl)leucyl)isoamylamine; D009195:Peroxidase; D003402:Creatine Kinase; D002154:Calpain; D007930:Leucine