Abstract: In order to evaluate the effects of calcium ion on calpalns mRNA expression and proteolysis activity,and muscle protein degradation,L6 myoblast and beef fascicle were used in vivo and in vitro samples respectively in this study.The results indicated thatμ-calpains activity increases when the calcium ions concentration is less than 500μmol/L,otherwise,theμ-calpains activity disappeares due to autolysis.The effects of calcium ion on m-calpain are less effective than onμ-calpain.Furthermore, calcium ion also accelerates the degradation of beef muscle proteins in vitro experiments,mRNA expressions ofμ-,and m-calpain both increases in L6 myoblast during the L6 had low death rate in vivo experiment.Therefore,it could be deduced that the calcium ion can not only activate calpains proteolysis activity and accelerate the degradation of muscle proteins,but also lead to mRNA expression ofμ-,and m-ealpain when the muscle cell is still alive.

Key words: calcium ions, calpains, proteolysis activity, mRNA, real-time quantitative PCR, casein zymography