K(V)2.1 channels mediate hypoxic inhibition of I(KV) in native pulmonary arterial smooth muscle cells of the rat.
OBJECTIVE
To determine whether, in native pulmonary arterial smooth muscle cells (PASMC), K(V)2.1 delayed-rectifying K(+) channels are central to the process of hypoxic pulmonary vasoconstriction.


METHODS
In this study, we tested for the presence of K(V)2.1 channel transcripts in rat small pulmonary arteries using RT-PCR, and for the protein itself using immunolocalisation. The contribution of K(V)2.1 channels to whole-cell K(V) currents (I(KV)) and their role in hypoxic inhibition of I(KV) in native PASMC was investigated utilising patch-clamp recordings.


RESULTS
K(V)2.1 mRNA expression and AbK(V)2.1 (anti-K(V)2.1 antibody) protein immunoreactivity were both present in small pulmonary arteries. Dialysis of PASMC with AbK(V)2.1 significantly attenuated I(KV) by 67% at +50 mV. Hypoxia ( approximately 20-30 mmHg) inhibited I(KV) by approximately 70% at +50 mV. Ablation of currents associated with K(V)2.1 using AbK(V)2.1 caused a marked reduction in the amplitude of I(KV). Hypoxia in the presence of the antibody did not affect the magnitude of I(KV).


CONCLUSIONS
These results indicate that K(V)2.1 channel subunits exist within small pulmonary arteries and conduct a significant part of I(KV) within native PASMC. Furthermore, application of AbK(V)2.1 abolishes hypoxic inhibition of I(KV) in native PASMC suggesting that K(V)2.1 channels play a pivotal role in mediating hypoxic pulmonary vasoconstriction.
Department of Pharmacology, School of Medical Sciences, University of Bristol, University Walk, Bristol, BS8 1TD, UK.
Dayle S
DS
Hogg
Andrew R L
AR
Davies
Gordon
G
McMurray
Roland Z
RZ
Kozlowski
D000818:Animals; D051668:Delayed Rectifier Potassium Channels; D004594:Electrophysiology; D015870:Gene Expression; D000860:Hypoxia / Q000503:physiopathology*; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000503:physiopathology*; D018408:Patch-Clamp Techniques; D015221:Potassium Channels / Q000032:analysis / Q000235:genetics / Q000502:physiology*; D024642:Potassium Channels, Voltage-Gated; D011651:Pulmonary Artery / Q000737:chemistry / Q000503:physiopathology*; D011652:Pulmonary Circulation; D012333:RNA, Messenger / Q000235:genetics; D051381:Rats; D017208:Rats, Wistar; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014661:Vasoconstriction
D051668:Delayed Rectifier Potassium Channels; D015221:Potassium Channels; D024642:Potassium Channels, Voltage-Gated; D012333:RNA, Messenger