Enzymatic studies on the skeletal myosin A and actomyosin of aging rats

Abstract

Myosin A and actomyosin were isolated from the skeletal muscle of old and young rats. The velocity of the Ca2+ activated myosin A ATPase was increased in the case of the older animals. On the other hand the velocity of the Mg2+ activated actomyosin ATPase was decreased in the skeletal muscle of the aging rats. At 5 x 10-5M ethylene glycol bis (β aminoethylether) concentration the inhibition of the Mg2+ activated myosin B ATPase of the 1 mth old rats was 2 to 3 fold smaller than that of the older animals. The myosin A component of the actomyosin was responsible for the decreased troponin inhibition in the case of the 1 mth old rats. Between the ages of 1 mth and 29 mth the number of free myosin A SH groups decreases by 50%. The lipid peroxidation in the muscle tissue of the 29 mth old rats was 3 fold greater than that in the muscle of the 1 mth old animals.