Myosins from rat right and left ventricles comparison of ATPase activities and light fragments released by 8 m-urea

Abstract

Myosins prepared from rat right and left ventricles had similar levels of ATPase activity, measured in Mg 2+ and in Ca 2+. The low molecular weight fragments of these myosins, examined by SDS-polyacrylamide gel electrophoresis, also did not differ. It is concluded that the differences between the mechanical characteristics of right- and left-ventricular contraction are not reflected in differences between the myosins of the two ventricles. However, the ATPase activity of rat cardiac myosin was higher than that noted previously for comparable preparations from rabbit and canine ventricles, and the low molecular weight fragments of rat cardiac myosin differed from those reported for rabbit cardiac myosin. These findings suggest that shortening velocity, which has been reported to be greater in the hearts of smaller animals, may reflect a difference in the low molecular weight fragments and ATPase activity of cardiac myosin.