The present study demonstrates that in the shrew ventricular muscle the speed of tension development and relaxation, as well as twitch duration, are much shorter than in the guinea-pig. It also shows that ventricular myosin of the shrrw has a high Ca2+-activated ATPase activity and that it is composed of α-type heavy chains. Namely, the native molecule is a V1 variety of myosin. These findings advance our knowledge on an as yet uncharacterized mammalian heart and further demonstrate the correlation between mechanical properties and myosin type in heart muscle.
- Isometric twitch characteristics
- Myosin ATPase
- Myosin heavy chains