title: Nitric oxide generation by isolated descending vasa recta.
abstract: Nitric oxide (NO) generation by the outer medullary descending vasa recta (OMDVR) was measured with the fluorescent dye 4,5-diaminofluoroscein (DAF-2) during 30-min incubations. Addition of 0.1 or 1.0 mM L-arginine to the incubation buffer increased the DAF-2 signal by 8.7 and 13.6% (P = 0.08 and P < 0.05), respectively. Compared with L-arginine alone (0.1 mM), bradykinin (BK; 1 x 10(-7) M) enhanced the DAF-2 signal by 11.1% (P < 0.05). The NO synthase inhibitor N(omega)-nitro-L-arginine methyl ester (0.1 mM) reversed the BK-stimulated NO generation as measured with either DAF-2 or by the oxidation of Fe(2+) hemoglobin. Using 1 mM 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl (tempol), a cell-permeant superoxide dismutase mimetic, we tested whether reduction of superoxide anion increases intracellular NO. Tempol increased DAF-2 fluorescence by 12 and 23.3%, respectively, over BK-stimulated or control vessels. Tempol also vasodilated ANG II (1 x 10(-8) M)-preconstricted OMDVR (P < 0.05). We conclude that NO generation by isolated OMDVR can be increased by L-arginine, that the endothelium-dependent vasodilator BK enhances NO production, and that NO consumption by superoxide plays a role in the determination of cellular NO concentrations.
authors.affiliation: Division of Nephrology, University of Maryland School of Medicine, Baltimore, Maryland 21201-1595.
authors.forename: K L
authors.initials: KL
authors.lastname: Rhinehart
authors.forename: T L
authors.initials: TL
authors.lastname: Pallone
mesh_terms: D000818:Animals; D000975:Antioxidants / Q000494:pharmacology; D001120:Arginine / Q000494:pharmacology; D001808:Blood Vessels / Q000187:drug effects / Q000378:metabolism; D001920:Bradykinin / Q000494:pharmacology; D003497:Cyclic N-Oxides / Q000494:pharmacology; D019793:Fluorescein; D066298:In Vitro Techniques; D007202:Indicators and Reagents; D007679:Kidney Medulla / Q000098:blood supply*; D009569:Nitric Oxide / Q000096:biosynthesis*; D009994:Osmolar Concentration; D051381:Rats; D017207:Rats, Sprague-Dawley; D013113:Spin Labels
chemical_list: C111205:4,5-diaminofluorescein; D000975:Antioxidants; D003497:Cyclic N-Oxides; D007202:Indicators and Reagents; D013113:Spin Labels; D009569:Nitric Oxide; D001120:Arginine; D001920:Bradykinin; D019793:Fluorescein; C001803:tempol