AJP - Heart and Circulatory Physiology, Vol 245, Issue 5 830-H839, Copyright © 1983 by American Physiological Society
Isolated myocytes from adult canine left ventricle: Ca2+ tolerance, electrophysiology, and ultrastructure
K. Hewett, M. J. Legato, P. Danilo Jr and R. B. Robinson
We have developed a method for isolating single cardiac muscle cells in
high yield (greater than 5 X 10(7) cells) from the canine left ventricle.
Most of the myocytes are single cells with ultrastructural detail
indistinguishable from intact ventricular myocardium, and more than 50% of
the isolated cells remain elongated for at least 7 h in 0.5 mM calcium.
Electrophysiological studies demonstrate that external potassium has a
strong influence on repolarization in the isolated ventricular cells.
Action potentials in [K+]o = 3.78 mM exhibit a positive over-shoot (greater
than zero potential), but repolarization often arrests at congruent to -35
mV unless driven to more negative potentials by hyperpolarizing current.
This phenomenon of two levels of resting potential is not observed at [K+]o
= 5.78 mM. At the higher potassium concentration, values for maximum
diastolic potential, amplitude, maximum rate of rise of phase 0, and action
potential duration all are similar to those of intact ventricular muscle.
However, the potential at the peak of the action potential plateau (phase
2) in the isolated myocyte is considerably more negative than that of
intact myocardium. In addition, there is a conspicuous notch between phases
1 and 2 of the action potential in the isolated myocyte, whereas the notch
is small or absent in intact myocardial action potentials. In summary, our
method results in a preparation of stable, ultrastructurally and
electrophysiologically intact cells, which should prove useful in studies
requiring a large and homogeneous population of myocardial cells.
