AJP - Heart and Circulatory Physiology, Vol 253, Issue 5 1018-H1025, Copyright © 1987 by American Physiological Society
Electrical restitution process in dispersed canine cardiac Purkinje and ventricular cells
R. B. Robinson, P. A. Boyden, B. F. Hoffman and K. W. Hewett
Department of Pharmacology, College of Physicians and Surgeons, Columbia University, New York, New York 10032.
Rate-dependent changes in cardiac action potential duration (APD) have been
related to ion accumulation and depletion in restricted extracellular
spaces. Isolated cardiac cells lack intercellular clefts and thus are less
likely than intact tissue to experience ionic transients immediately
outside the plasma membrane. Furthermore, isolated Purkinje cells lack the
T tubules found in ventricular tissue and cells, which also can be a site
of ion accumulation and depletion. We therefore employed single canine
ventricular and Purkinje cells to investigate the contribution of
restricted spaces to the electrical restitution process. In both cell
types, abrupt changes in cycle length do not alter resting potential, but
APD alters with a time constant of approximately 1 min. In addition, both
preparations exhibit two components to the electrical restitution process
of the APD. The rapid component has a time constant of 66 +/- 17 ms in the
ventricle cells and 186 +/- 43 ms in the Purkinje cells. The slower
component is both smaller and more variable. These values are similar to
those reported in intact canine ventricular and Purkinje tissue. Thus the
restitution process of APD, as measured in these isolated cardiac cells, is
not markedly dependent on the presence or absence of restricted
extracellular spaces.
