Preferential expression and function of voltage-gated, O2-sensitive K+ channels in resistance pulmonary arteries explains regional heterogeneity in hypoxic pulmonary vasoconstriction: ionic diversity in smooth muscle cells.
Hypoxic pulmonary vasoconstriction (HPV) is initiated by inhibition of O2-sensitive, voltage-gated (Kv) channels in pulmonary arterial smooth muscle cells (PASMCs). Kv inhibition depolarizes membrane potential (E(M)), thereby activating Ca2+ influx via voltage-gated Ca2+ channels. HPV is weak in extrapulmonary, conduit pulmonary arteries (PA) and strong in precapillary resistance arteries. We hypothesized that regional heterogeneity in HPV reflects a longitudinal gradient in the function/expression of PASMC O2-sensitive Kv channels. In adult male Sprague Dawley rats, constrictions to hypoxia, the Kv blocker 4-aminopyridine (4-AP), and correolide, a Kv1.x channel inhibitor, were endothelium-independent and greater in resistance versus conduit PAs. Moreover, HPV was dependent on Kv-inhibition, being completely inhibited by pretreatment with 4-AP. Kv1.2, 1.5, Kv2.1, Kv3.1b, Kv4.3, and Kv9.3. mRNA increased as arterial caliber decreased; however, only Kv1.5 protein expression was greater in resistance PAs. Resistance PASMCs had greater K+ current (I(K)) and a more hyperpolarized E(M) and were uniquely O2- and correolide-sensitive. The O2-sensitive current (active at -65 mV) was resistant to iberiotoxin, with minimal tityustoxin sensitivity. In resistance PASMCs, 4-AP and hypoxia inhibited I(K) 57% and 49%, respectively, versus 34% for correolide. Intracellular administration of anti-Kv1.5 antibodies inhibited correolide's effects. The hypoxia-sensitive, correolide-insensitive I(K) (15%) was conducted by Kv2.1. Anti-Kv1.5 and anti-Kv2.1 caused additive depolarization in resistance PASMCs (Kv1.5>Kv2.1) and inhibited hypoxic depolarization. Heterologously expressed human PASMC Kv1.5 generated an O2- and correolide-sensitive I(K) like that in resistance PASMCs. In conclusion, Kv1.5 and Kv2.1 account for virtually all the O2-sensitive current. HPV occurs in a Kv-enriched resistance zone because resistance PASMCs preferentially express O2-sensitive Kv-channels.
Archer
Stephen L
SL
Heart and Stroke Chair in Cardiovascular Research, Cardiology Division, Department of Medicine, University of Alberta, WMC 2C2.36, 8440 112th St, Edmonton, Alberta T6G 2B7, Canada. sarcher@cha.ab.ca
Wu
Xi-Chen
XC
Thébaud
Bernard
B
Nsair
Ali
A
Bonnet
Sebastien
S
Tyrrell
Ben
B
McMurtry
M Sean
MS
Hashimoto
Kyoko
K
Harry
Gwyneth
G
Michelakis
Evangelos D
ED
D015761:4-Aminopyridine / Q000494:pharmacology; D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D015687:Cell Hypoxia; D002478:Cells, Cultured / Q000187:drug effects / Q000502:physiology; D005786:Gene Expression Regulation; D006801:Humans; D000860:Hypoxia / Q000503:physiopathology*; D015640:Ion Channel Gating / Q000187:drug effects; D017136:Ion Transport / Q000187:drug effects; D051666:Kv1.5 Potassium Channel; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000473:pathology*; D032389:Myocytes, Smooth Muscle / Q000187:drug effects / Q000502:physiology*; D010100:Oxygen / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D010455:Peptides / Q000494:pharmacology; D011188:Potassium / Q000378:metabolism; D024642:Potassium Channels, Voltage-Gated / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D011651:Pulmonary Artery / Q000473:pathology*; D011652:Pulmonary Circulation / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D011993:Recombinant Fusion Proteins / Q000502:physiology; D012604:Scorpion Venoms / Q000494:pharmacology; D051669:Shab Potassium Channels; D014161:Transduction, Genetic; D014315:Triterpenes / Q000494:pharmacology; D014655:Vascular Resistance / Q000187:drug effects / Q000502:physiology*; D014661:Vasoconstriction / Q000187:drug effects / Q000502:physiology*
C496981:KCNA5 protein, human; C496983:Kcna5 protein, rat; C496991:Kcnb1 protein, rat; D051666:Kv1.5 Potassium Channel; D010455:Peptides; D024642:Potassium Channels, Voltage-Gated; D011993:Recombinant Fusion Proteins; D012604:Scorpion Venoms; D051669:Shab Potassium Channels; D014315:Triterpenes; C118657:correolide; C003609:tityustoxin; C064719:iberiotoxin; D015761:4-Aminopyridine; D000109:Acetylcholine; D011188:Potassium; D010100:Oxygen