NDLI: Human Kir2.1 channel carries a transient outward potassium current with inward rectification

Content Provider	Springer Nature Link
Author	Zhang, De Yong Lau, Chu Pak Li, Gui Rong
Copyright Year	2008
Abstract	We have previously reported a depolarization-activated 4-aminopyridine-resistant transient outward K+ current with inward rectification (I to.ir) in canine and guinea pig cardiac myocytes. However, molecular identity of this current is not clear. The present study was designed to investigate whether Kir2.1 channel carries this current in stably transfected human embryonic kidney (HEK) 293 cells using whole-cell patch-clamp technique. It was found that HEK 293 cells stably expressing human Kir2.1 gene had a transient outward current elicited by voltage steps positive to the membrane potential (around −70 mV). The current exhibited a current–voltage relationship with intermediate inward rectification and showed time-dependent inactivation and rapid recovery from inactivation. The half potential (V 0.5) of availability of the current was −49.4 ± 2.1 mV at 5 mM K+ in bath solution. Action potential waveform clamp revealed two components of outward currents; one was immediately elicited and then rapidly inactivated during depolarization, and another was slowly activated during repolarization of action potential. These properties were similar to those of I to.ir observed previously in native cardiac myocytes. Interestingly, inactivation of the I to.ir was strongly slowed by increasing intracellular free Mg2+ (Mg2+ i , from 0.03 to 1.0, 4.0, and 8.0 mM). The component elicited by action potential depolarization increased with the elevation of Mg2+ i . Inclusion of spermine (100 μM) in the pipette solution remarkably inhibited both the I to.ir and steady-state current. These results demonstrate that the Mg2+ i -dependent current carried by Kir2.1 likely is the molecular identity of I to.ir observed previously in cardiac myocytes.
Starting Page	1275
Ending Page	1285
Page Count	11
File Format	PDF
ISSN	00316768
Journal	Pflügers Archiv
Volume Number	457
Issue Number	6
e-ISSN	14322013
Language	English
Publisher	Springer-Verlag
Publisher Date	2008-11-11
Publisher Place	Berlin, Heidelberg
Access Restriction	One Nation One Subscription (ONOS)
Subject Keyword	Kir2.1 channel Inward rectification I K1 Transient outward current with inward rectification Human Physiology
Content Type	Text
Resource Type	Article
Subject	Physiology Physiology (medical) Clinical Biochemistry

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