AJP - Heart and Circulatory Physiology, Vol 243, Issue 3 391-H397, Copyright © 1982 by American Physiological Society
Comparative force-velocity relation and analyses of myosin of dog atria and ventricles
J. Wikman-Coffelt, H. Refsum, G. Hollosi, L. Rouleau, L. Chuck and W. W. Parmley
The isolated muscle and purified myofibrillar proteins of canine atria and
ventricles were compared relative to force-velocity relations and rate of
adenosine 5'-triphosphatase (ATPase) activity as a function of calcium
concentrations. The maximal stress development of isolated trabeculae of
canine atria was similar to that of canine right ventricular papillary
muscles when analyzed at saturating calcium concentrations (7.5 mM);
however, stress was less in the atria when studied at normal calcium
concentrations (2.5 mM). The maximal velocity of shortening of atrial
trabeculae was about 2.3 times higher than that of ventricular muscle.
Regulated actomyosin characterized from the myofibrillar proteins of the
two tissues gave directionally similar calcium sensitivity. The maximum
velocity of shortening for actin-activated atrial myosin of the dog was
approximately 1.8 times higher when the latter was analyzed as a function
of actin concentration. Both maximal tension of isolated muscle and
regulated actomyosin ATPase activity were dependent on calcium
concentration.
