AJP - Heart and Circulatory Physiology, Vol 249, Issue 1 108-H121, Copyright © 1985 by American Physiological Society
A re-examination of late outward plateau currents of cardiac Purkinje fibers
J. M. Jaeger and W. R. Gibbons
Two outward currents, IX1 and IX2, are thought to be activated by
depolarization of the Purkinje fiber. One of these, IX1, is presently
believed to play a critical role in repolarization of the action potential.
The IX currents were originally analyzed in voltage-clamp experiments in
sheep Purkinje fibers. These experiments were designed to minimize
interference by other currents, and it was assumed that changes of the net
current were produced entirely by the IX currents. We have tried to repeat
the original experiments and the analysis that led to acceptance of the
existence and roles of the IX currents, without success. Moreover, tests of
how membrane current should behave if the IX current hypothesis is correct
did not give satisfactory results. Our data suggest the original
conclusions about IX1 and IX2 may need substantial revision.
