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The calpastatin/calpain system in trout Salmo trutta trutta muscle

Many recent reports suggest that the calpastatin/calpain system plays a role in cellular growth and differentiation. Defects of the calpastatin/calpain system have been linked to cellular dysfunctions, apoptosis, myocardial infarct, and dystrophies. The calpastatin/calpain system has also been implicated in post-mortem tenderization of skeletal muscle through degradation of key myofibrillar and associated proteins, a process of key importance to meat quality. In the present study we investigate the presence and activity of the calpastatin/calpain system in trout muscle samples, collected at 0, 3, 18 and 28 h post-mortem, by immunohistochemistry method. Calpastatin is a specific endogenous enzyme of cytosol, modulating the ubiquitous calpains. Calpastatin was found in samples obtained in vivo and immediately post-mortem, but its concentration declined rapidly in samples obtained 3, 18 and 28 h post-mortem. The ubiquitous m e m-calpains, which are localized on Z line proteins and activated by intracellular Ca2+ increase, showed a rapid decline within 3 h post-mortem. By contrast p94 calpain, which is specific to skeletal muscle, showed a slow decrease post-mortem which was independent of intracellular Ca2+ increase. Our results suggest that the mechanism of activation and activity of the calpastatin/calpain system in trout is similar to that described in mammals.