Real-time profiling of kidney tubular fluid nitric oxide concentrations in vivo.
To directly determine intratubular nitric oxide concentrations ([NO]) in vivo, we modified amperometric integrated electrodes (WPI P/N ISO-NOP007), which are highly sensitive to NO and not affected by ascorbic acid, nitrite, L-arginine, or dopamine. Although reactive lengths were as short as 5 microm long, the electrode still responded rapidly. With the use of kidney surface fluid as the "zero point," the electrode tip was inserted into tubular segments along the track of a perforation made by a beveled glass pipette. The surface fluid zero point was usually stable as distal, late proximal, and early proximal tubule [NO] levels were measured sequentially in the same nephron. In eight normal rats, distal, late proximal, and early proximal [NO] concentrations were each approximately 110 nM. In contrast, in nine 5/6 nephrectomized rats 2 wk postsurgery, although [NO] also did not differ among distal, late proximal, and early proximal segments, levels were approximately fourfold higher than those in normal rats and were significantly reduced after N(G)-monomethyl-L-arginine administration. These are the first quantitative in vivo tubular fluid [NO] measurements and show a significant increase in tubular fluid [NO] after renal ablation.
Levine
D Z
DZ
Division of Nephrology, The Kidney Research Centre, Ottawa Health Research Institute, and University of Ottawa, Ottawa, Ontario, Canada K1H 8M5.
Iacovitti
M
M
Burns
K D
KD
Zhang
X
X
D000818:Animals; D004566:Electrodes; D004791:Enzyme Inhibitors / Q000494:pharmacology; D007686:Kidney Tubules, Distal / Q000378:metabolism*; D007687:Kidney Tubules, Proximal / Q000378:metabolism*; D009392:Nephrectomy; D009569:Nitric Oxide / Q000032:analysis / Q000378:metabolism* / Q000652:urine; D010477:Perfusion; D051381:Rats; D013997:Time Factors; D019323:omega-N-Methylarginine / Q000494:pharmacology
D004791:Enzyme Inhibitors; D019323:omega-N-Methylarginine; D009569:Nitric Oxide