The relation between myosin Ca 2+- and K +-adenosine triphosphatase activity of heart muscles in mammals of different size

Abstract

1. 1. The influence of KCl and CaCl 2 on ATPase activity of ventricular myosin of the mouse, rat, rabbit and cow, the temperature dependence of ATPase and the effect of pCMB treatment and tryptic digestion on ATPase activity of these myosins were studied. 2. 2. Ca 2+- and K +-ATPase activities of myosins were inversely related to body size of the animal species; when K +-ATPase activities were measured in the absence of EDTA, the body size/ATPase dependence was only slightly apparent. 3. 3. The influence of temperature, the effect of pCMB and the influence of tryptic digestion on Ca 2+-ATPase activity distinguished the compared myosins. 4. 4. There was a marked alteration of the effect of myosin treatment with pCMB or trypsin on K +-ATPase activity of these myosins and in this case differences in K +-ATPase activities were less pronounced.