title: Intrinsic nitric oxide and superoxide production regulates descending vasa recta contraction.
abstract: Descending vasa recta (DVR) are 12- to 15-μm microvessels that supply the renal medulla with blood flow. We examined the ability of intrinsic nitric oxide (NO) and reactive oxygen species (ROS) generation to regulate their vasoactivity. Nitric oxide synthase (NOS) inhibition with N(ω)-nitro-l-arginine methyl ester (l-NAME; 100 μmol/l), or asymmetric N(G),N(G)-dimethyl-l-arginine (ADMA; 100 μmol/l), constricted isolated microperfused DVR by 48.82 ± 4.34 and 27.91 ± 2.91%, respectively. Restoring NO with sodium nitroprusside (SNP; 1 mmol/l) or application of 8-Br-cGMP (100 μmol/l) reversed DVR vasoconstriction by l-NAME. The superoxide dismutase mimetic Tempol (1 mmol/l) and the NAD(P)H inhibitor apocynin (100, 1,000 μmol/l) also blunted ADMA- or l-NAME-induced vasoconstriction, implicating a role for concomitant generation of ROS. A role for ROS generation was also supported by an l-NAME-associated rise in oxidation of dihydroethidium that was prevented by Tempol or apocynin. To test whether H(2)O(2) might play a role, we examined its direct effects. From 1 to 100 μmol/l, H(2)O(2) contracted DVR whereas at 1 mmol/l it was vasodilatory. The H(2)O(2) scavenger polyethylene glycol-catalase reversed H(2)O(2) (10 μmol/l)-induced vasoconstriction; however, it did not affect l-NAME-induced contraction. Finally, the previously known rise in DVR permeability to (22)Na and [(3)H]raffinose that occurs with luminal perfusion was not prevented by NOS blockade. We conclude that intrinsic production of NO and ROS can modulate DVR vasoactivity and that l-NAME-induced vasoconstriction occurs, in part, by modulating superoxide concentration and not through H(2)O(2) generation. Intrinsic NO production does not affect DVR permeability to hydrophilic solutes.
authors: Div. of Nephrology, N3W143, 22 S. Greene St., UMMS, Baltimore, MD 21201, USA. ccao@medicine.umaryland.edu
authors: Chunhua
authors: C
authors: Cao
authors: Aurélie
authors: A
authors: Edwards
authors: Mauricio
authors: M
authors: Sendeski
authors: Whaseon
authors: W
authors: Lee-Kwon
authors: Lan
authors: L
authors: Cui
authors: Chun-Yu
authors: CY
authors: Cai
authors: Andreas
authors: A
authors: Patzak
authors: Thomas L
authors: TL
authors: Pallone
mesh_terms: D000818:Animals; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004996:Ethidium / Q000031:analogs & derivatives; D005456:Fluorescent Dyes; D006861:Hydrogen Peroxide / Q000494:pharmacology; D007150:Immunohistochemistry; D007202:Indicators and Reagents; D009129:Muscle Tonus / Q000502:physiology; D009131:Muscle, Smooth, Vascular / Q000502:physiology; D019255:NADPH Oxidases / Q000037:antagonists & inhibitors; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009569:Nitric Oxide / Q000096:biosynthesis* / Q000502:physiology*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors; D016877:Oxidants / Q000494:pharmacology; D010084:Oxidation-Reduction; D010539:Permeability; D051381:Rats; D017207:Rats, Sprague-Dawley; D017382:Reactive Oxygen Species / Q000378:metabolism; D012079:Renal Circulation / Q000187:drug effects / Q000502:physiology*; D013481:Superoxides / Q000378:metabolism*; D014661:Vasoconstriction / Q000187:drug effects / Q000502:physiology*
chemical_list: D004791:Enzyme Inhibitors; D005456:Fluorescent Dyes; D007202:Indicators and Reagents; D016877:Oxidants; D017382:Reactive Oxygen Species; C067883:dihydroethidium; D013481:Superoxides; D009569:Nitric Oxide; D006861:Hydrogen Peroxide; D019001:Nitric Oxide Synthase; D019255:NADPH Oxidases; D004996:Ethidium; D019331:NG-Nitroarginine Methyl Ester