Myosin ATPase in swine heart, "soleus" and "gastrocnemius"

Myosin was isolated from heart ventricle, soleus and gastrocnemius of freshly slaughtered swine. ATPase activities (mu moles Pi/mg/min) were found to be higher in heart muscle (Ca++ activated = .39 +/- .04; EDTA activated = .59 +/- .06) than in ST soleus (Ca++ activated = .23 +/- .02; EDTA activated = .48 +/- .05) or FT gastrocnemius (Ca++ activated = .32 +/- .03; EDTA activated = .52 +/- .04). The results suggest that the myosin of swine cardiac muscle is different from the myosin of skeletal muscle, or at least, the rate of hydrolysis of ATP on the myosin sites is different between these tissues. There is a difference in relationship of ATPase between heart and skeletal muscle in swine compared to that seen in other mammalian species.