title: Vasa recta pericytes express a strong inward rectifier K+ conductance.
abstract: Strong inward rectifier potassium channels are expressed by some vascular smooth muscle cells and facilitate K+-induced hyperpolarization. Using whole cell patch clamp of isolated descending vasa recta (DVR), we tested whether strong inward rectifier K+ currents are present in smooth muscle and pericytes. Increasing extracellular K+ from 5 to 50 and 140 mmol/l induced inward rectifying currents. Those currents were Ba2+ sensitive and reversed at the K+ equilibrium potential imposed by the electrode and extracellular buffers. Ba2+ binding constants in symmetrical K+ varied between 0.24 and 24 micromol/l at -150 and -20 mV, respectively. Ba2+ blockade was time and voltage dependent. Extracellular Cs+ also blocked the inward currents with binding constants between 268 and 4,938 micromol/l at -150 and -50 mV, respectively. Ba2+ (30 micromol/l) and ouabain (1 mmol/l) depolarized pericytes by an average of 11 and 24 mV, respectively. Elevation of extracellular K+ from 5 to 10 mmol/l hyperpolarized pericytes by 6 mV. That hyperpolarization was reversed by Ba2+ (30 micromol/l). We conclude that strong inward rectifier K+ channels and Na+-K+-ATPase contribute to resting potential and that KIR channels can mediate K+-induced hyperpolarization of DVR pericytes.
authors.affiliation: Division of Nephrology, Department of Medicine, N3W143, 22 S. Greene St., University of Maryland, School of Medicine, Baltimore, MD 21201, USA.
authors.forename: Chunhua
authors.initials: C
authors.lastname: Cao
authors.forename: Jae Hwan
authors.initials: JH
authors.lastname: Goo
authors.forename: Whaseon
authors.initials: W
authors.lastname: Lee-Kwon
authors.forename: Thomas L
authors.initials: TL
authors.lastname: Pallone
mesh_terms: D000818:Animals; D001464:Barium / Q000494:pharmacology; D002196:Capillaries / Q000166:cytology / Q000502:physiology*; D002586:Cesium / Q000494:pharmacology; D004594:Electrophysiology; D066298:In Vitro Techniques; D007679:Kidney Medulla / Q000098:blood supply; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D010042:Ouabain / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D020286:Pericytes / Q000378:metabolism / Q000502:physiology*; D011188:Potassium / Q000378:metabolism; D024661:Potassium Channels, Inwardly Rectifying / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D024661:Potassium Channels, Inwardly Rectifying; D002586:Cesium; D001464:Barium; D010042:Ouabain; D011188:Potassium