Different Expression of Calpains/Calpastatin in Rat Gastrocnemius Muscle after Repeated Exercise

Abstract

Objectives: Calpains/calpastatin degrades skeletal muscle proteins in vitro. However, no evidence shows changes in the expression pattern of calpains/calpastatin after exercises with different intensities and durations. The objective of this study was to investigate the alteration of μ-, m-, n-calpain, and calpastatin expression after repeated exercises, and its potential association between muscle injury and exercise intensity.

Methods: Rats were divided into nonexercise control and repeated exercise [RE] groups. The RE group was further divided into high- and moderate-intensity exercise subgroups. Each group exercised for three, five, seven, and nine weeks, respectively.

Results: There were no significant changes found in mRNA expression of m- and μ-calpain. The n-calpain and calpastatin mRNA expressions are basically consistent with their protein levels. The m-calpain level and calpastatin protein expression increased after three and five weeks of repeated exercise training, respectively. However, both n-calpain protein expression and μ-calpain level generally decreased with time.

Conclusions: The increased m-calpain level promotes muscle injury and calpastatin protein expression might execute a protective function for muscle injury. The changes of μ-calpain level might serve as a useful predictor of muscle injury. Our findings also suggested that repeated exercise trigger muscle adaptations to prevent potential future exercise-induced injury.

KEYWORDS:

• Calpains
• calpastatin
• repeated exercise
• skeletal muscle