AJP - Cell Physiology, Vol 262, Issue 5 C1266-C1272, Copyright © 1992 by American Physiological Society
Developmental increases in the inwardly rectifying potassium current of rat ventricular myocytes
G. M. Wahler
Department of Physiology and Biophysics, University of Illinois, Chicago 60680.
The neonatal rat ventricular action potential has a shape similar to that
of most adult mammals. However, shortly after birth, the action potential
shortens to a spike-like configuration. The contribution of changes in
repolarizing currents to the shortening is unclear. Thus the inwardly
rectifying potassium current (IK1) was measured in heart cells from rats of
varying ages using patch-clamp techniques. In freshly isolated cells, whole
cell IK1 currents increased greatly between ages 3 and 9-13 days and
remained constant thereafter. In culture, IK1 disappeared preferentially in
older cells, obscuring the developmental increase. Age-dependent
differences in single-channel activity were also observed. Adult cells had
IK1 channels consisting of two populations (30 and 42 pS), whereas neonatal
cells exhibited only the lower conductance channel. The appearance of the
42-pS channel may contribute a part of the developmental increase in IK1.
It was concluded that IK1 increases during postnatal development of the rat
ventricle and that this increase may contribute to the postnatal shortening
of the rat ventricular action potential.
