Abstract
[Purpose] The aim of the present study was to determine whether the expression of mitogen-activated protein kinase (MAPK) isoforms is related to cast-immobilization-induced atrophy in rat skeletal muscles. [Subjects] The subjects were 24 male Sprague-Dawley rats aged 7 weeks old. [Methods] The rats were randomly divided into a control group (n=4) and four experimental groups (n=20). The experimental groups were submitted to 3, 7, 14, or 21 days of cast-immobilization to provoke disuse atrophy. [Results] The weights and cross-sectional areas of the cast-immobilized muscles were significantly lower than those of the non-immobilized controls. The PKB/Akt and ERK1/2 phosphorylation in atrophied muscles was significantly lower than those in the non-immobilized controls. However, cast immobilization increased the phosphorylation of p38 MAPK and SAPK/JNK. [Conclusion] These results suggest that cast immobilization-induced atrophy may be mediated by the activation of the ERK1/2, p38 MAPK, and SAPK/JNK pathways, and that the MAPK isoforms are differently regulated by the PKB/Akt pathway during atrophy in the gastrocnemius muscle.
