Detection of muscle-specific creatine kinase expression as physiological indicator for Atlantic salmon (Salmo salar L) skeletal muscle damage

Plasma creatine kinase (CK) release is a marker of damage in fish; their expression can indicate drug/contaminant exposure. Three CK isoforms have been described in fish: muscle CK (M-CK), brain CK (B-CK) and mitochondrial sarcomeric, and the release of any of them could be detected in the serum. Nevertheless, the expression and properties of M-CK in Atlantic salmon are still unknown. In this study, we evaluated differential M-CK expression in Atlantic salmon (Salmo salar L) skeletal muscle and serum at 0, 5, 10, and 15 days post-infection (dpi) with the infectious salmon anaemia virus, a primary aquaculture pathogen in Chile. The M-CK isoform was assessed using a Western blot-validated antibody. Results for qPCR (+10.8 AU) and ELISA (1.24, p < 0.05) showed increased skeletal muscle M-CK at 10 dpi (r = 0.9817, p < 0.05). Serum M-CK significantly increased at 5 and 10 dpi (r = 1.26 and 1.17, p < 0.05). In situ M-CK detection in the myofibrils showed co-localization with the pro-inflammatory cytokine IL-1β particularly at 10 dpi. In summary, serum M-CK detection apparently serves as a non-invasive, functional indicator for Atlantic salmon skeletal muscle damage, which could indicate disease or environmental stress.