Role of heat stress-induced activation of calcineurin in skeletal muscle hypertrophy of rats

Abstract

Calcineurin plays important signaling pathways in gene regulation and biological responses to external stimuli in many organisms and in many types of cell. Recently, we found that heat stress induced the increment of calcineurin expression and hypertrophy in skeletal muscle in vivo. However, the precise role of a calcineurin-dependent signaling pathway in skeletal muscle hypertrophy is still unclear. Therefore, this study was carried out to elucidate a role of a calcineurin-dependent signaling pathway in heat stress-induced muscle hypertrophy. Wistar strain male rats were divided into three groups; control (CC), heat stress (HC) and heat stress with the inhibition of calcineurin by using cyclosporine A (HI), a potent inhibitor for calcineurin. The heat-stressed groups were exposed to environmental heat stress (41°C for 60 min). Injection of cyclosporine A was administrated for animals in HI group once a day for 14 days. Soleus and extensor digitorum longus muscles were dissected from both hindlimbs 1, 7 and 14 days after heat exposure. Effects of inhibitions of calcineurin on heat-stresses muscle hypertrophy were evaluated. A partial depression of heat stress-associated muscle hypertrophy was observed in rats with inhibition of calcineurin expression. [Jpn J Physiol 54 Suppl:S119 (2004)]