Effects of hemodynamic overload on canine myocardial myosin.

After mild banding of pulmonary artery in dogs there was a rapid elevation in protein and RNA synthesis, followed by an elevation in myosin content and myosin ATPase activity. There was an increase in myosin ATPase activity when K+ or Ca++ was used as activator effector but not with the cations, Mn++ or NH4+. Concomitant with an increase in myosin ATPase activity there was a decrease in one of the C1 light chain components, previously named C1d.