Single herg delayed rectifier k+ channels expressed in xenopus
oocytes.
Zou, Anruo, Mark E. Curran, Mark T. Keating, and Michael C.
Sanguinetti.
Cardiology Division, and Eccles Program in Human Molecular Biology
and Genetics, Department of Human Genetics, Howard Hughes Medical
Institute, University of Utah Health Sciences Center, Salt Lake City,
UT 84132
APStracts 3:0460H, 1996.
HERG is a K+ channel with properties similar to IKr, a delayed
rectifier K+ current important for repolarization of human cardiac
myocytes. In this study, we have characterized the single channel
properties of HERG expressed in Xenopus oocytes. Currents were
measured in cell-attached patches with an extracellular [K+] of 120
mM. The single HERG channel conductance determined at test potentials
between -50 and -110 mV was 12.1 +/- 0.6 pS. At positive test
potentials (+40 to +80 mV), the probability of channel opening was
low and the slope conductance was 5.1 +/- 0.6 pS. The mean channel
open times at -90 mV were 2.9 +/- 0.5 and 11.8 +/- 1.0 ms, and the
mean channel closed times were 0.54 +/- 0.02 and 14.5 +/- 5.3 ms.
Single HERG channels were blocked by MK-499, a class III
antiarrhythmic agent that blocks IKr in cardiac myocytes. The
development of block was more rapid in inside-out patches than in
cell-attached patches or in whole-cell recordings, indicating that
block occurs from the cytoplasmic side of the membrane. The single
channel properties of HERG are similar to IKr channels of isolated
cardiac myocytes, providing further evidence that HERG proteins
coassemble to form IKr channels.
Received 13 May 1996; accepted in final form 24 September 1996.
APS Manuscript Number H429-6.
Article publication pending Am. J. Physiol. (Heart Circ. Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 13 November 1996