title: Mural propagation of descending vasa recta responses to mechanical stimulation.
abstract: To investigate the responses of descending vasa recta (DVR) to deformation of the abluminal surface, we devised an automated method that controls duration and frequency of stimulation by utilizing a stream of buffer from a micropipette. During stimulation at one end of the vessel, fluorescent responses from fluo4 or bis[1,3-dibutylbarbituric acid-(5)] trimethineoxonol [DiBAC₄(3)], indicating cytoplasmic calcium ([Ca²⁺]CYT) or membrane potential, respectively, were recorded from distant cells. Alternately, membrane potential was recorded from DVR pericytes by nystatin whole cell patch-clamp. Mechanical stimulation elicited reversible [Ca²⁺)]CYT responses that increased with frequency. Individual pericyte responses along the vessel were initiated within a fraction of a second of one another. Those responses were inhibited by gap junction blockade with 18 β-glycyrrhetinic acid (100 μM) or phosphoinositide 3 kinase inhibition with 2-morpholin-4-yl-8-phenylchromen-4-one (50 μM). [Ca²⁺]CYT responses were blocked by removal of extracellular Ca²⁺ or L-type voltage-gated channel blockade with nifedipine (10 μM). At concentrations selective for the T-type channel blockade, mibefradil (100 nM) was ineffective. During mechanostimulation, pericytes rapidly depolarized, as documented with either DiBAC4(3) fluorescence or patch-clamp recording. Single stimuli yielded depolarizations of 22.5 ± 2.2 mV while repetitive stimuli at 0.1 Hz depolarized pericytes by 44.2 ± 4.0 mV. We conclude that DVR are mechanosensitive and that rapid transmission of signals along the vessel axis requires participation of gap junctions, L-type Ca²⁺ channels, and pericyte depolarization.
authors.affiliation: Division of Nephrology, Department of Medicine, University of Maryland School of Medicine, Baltimore, MD 21201, USA.
authors.forename: Zhong
authors.initials: Z
authors.lastname: Zhang
authors.forename: Kristie
authors.initials: K
authors.lastname: Payne
authors.forename: Chunhua
authors.initials: C
authors.lastname: Cao
authors.forename: Thomas L
authors.initials: TL
authors.lastname: Pallone
mesh_terms: D000818:Animals; D002121:Calcium Channel Blockers / Q000494:pharmacology; D020746:Calcium Channels, L-Type / Q000378:metabolism; D020013:Calcium Signaling / Q000502:physiology; D002462:Cell Membrane / Q000187:drug effects; D016764:Cell Polarity / Q000187:drug effects; D002867:Chromones / Q000494:pharmacology; D003593:Cytoplasm / Q000378:metabolism; D005456:Fluorescent Dyes; D017629:Gap Junctions / Q000502:physiology; D066298:In Vitro Techniques; D008856:Microscopy, Fluorescence; D009025:Morpholines / Q000494:pharmacology; D018919:Neovascularization, Physiologic / Q000502:physiology*; D009543:Nifedipine / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D020286:Pericytes / Q000187:drug effects; D010812:Physical Stimulation; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D012079:Renal Circulation / Q000502:physiology*
chemical_list: D002121:Calcium Channel Blockers; D020746:Calcium Channels, L-Type; D002867:Chromones; D005456:Fluorescent Dyes; D009025:Morpholines; D047428:Protein Kinase Inhibitors; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; D009543:Nifedipine
keywords: calcium; electrophysiology; kidney; medulla; microcirculation; rat