Flow-mediated dilatation (FMD) of the brachial artery assessed by high-resolution ultrasound is widely used to measure endothelial function. However, the technique is not standardized, with different groups using occlusion of either the wrist or the upper arm to induce increased blood flow. The validity of the test as a marker of endothelial function rests on the assumption that the dilatation observed is endothelium-dependent and mediated by nitric oxide (NO). We sought to compare the NO component of brachial artery dilatation observed following wrist or upper arm occlusion. Dilatation was assessed before and during intra-arterial infusion of the NO synthase inhibitor NG-monomethyl-l-arginine (l-NMMA) following occlusion of (i) the wrist (distal to ultrasound probe) and (ii) the upper arm (proximal to ultrasound probe) for 5min in ten healthy males. Dilatation was significantly greater after upper arm occlusion (upper arm, 11.62±3.17%; wrist, 7.25±2.49%; P = 0.003). During l-NMMA infusion, dilatation after wrist occlusion was abolished (from 7.25±2.49% to 0.16±2.24%; P < 0.001), whereas dilatation after upper arm occlusion was only partially attenuated (from 11.62±3.17% to 7.51±2.34%; P = 0.006). The peak flow stimulus was similar after wrist and upper arm occlusion. We conclude that dilatation following upper arm occlusion is greater than that observed after wrist occlusion, despite a similar peak flow stimulus. l-NMMA infusion revealed that FMD following wrist occlusion is mediated exclusively by NO, while dilatation following upper arm occlusion comprises a substantial component not mediated by NO, most probably related to tissue ischaemia around the brachial artery. FMD following wrist occlusion may be a more valid marker of endothelial function than dilatation following upper arm occlusion.
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Research Article|
November 20 2001
Flow-mediated dilatation following wrist and upper arm occlusion in humans: the contribution of nitric oxide
Sagar N. DOSHI;
Sagar N. DOSHI
*Department of Pharmacology, Cardiovascular Sciences Research Group, Wales Heart Research Institute, University of Wales College of Medicine, Heath Park, Cardiff CF14 4XN, U.K.
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Katerina K. NAKA;
Katerina K. NAKA
†Department of Cardiology, Cardiovascular Sciences Research Group, Wales Heart Research Institute, University of Wales College of Medicine, Heath Park, Cardiff CF14 4XN, U.K.
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Nicola PAYNE;
Nicola PAYNE
‡Department of Medical Computing and Statistics, University of Wales College of Medicine, Heath Park, Cardiff CF14 4XN, U.K.
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Christopher J.H. JONES;
Christopher J.H. JONES
†Department of Cardiology, Cardiovascular Sciences Research Group, Wales Heart Research Institute, University of Wales College of Medicine, Heath Park, Cardiff CF14 4XN, U.K.
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Moira ASHTON;
Moira ASHTON
†Department of Cardiology, Cardiovascular Sciences Research Group, Wales Heart Research Institute, University of Wales College of Medicine, Heath Park, Cardiff CF14 4XN, U.K.
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Malcolm J. LEWIS;
Malcolm J. LEWIS
*Department of Pharmacology, Cardiovascular Sciences Research Group, Wales Heart Research Institute, University of Wales College of Medicine, Heath Park, Cardiff CF14 4XN, U.K.
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Jonathan GOODFELLOW
†Department of Cardiology, Cardiovascular Sciences Research Group, Wales Heart Research Institute, University of Wales College of Medicine, Heath Park, Cardiff CF14 4XN, U.K.
Correspondence: Dr J Goodfellow (e-mail [email protected]).
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Publisher: Portland Press Ltd
Received:
January 22 2001
Revision Received:
May 14 2001
Accepted:
July 18 2001
Online ISSN: 1470-8736
Print ISSN: 0143-5221
The Biochemical Society and the Medical Research Society © 2001
2001
Clin Sci (Lond) (2001) 101 (6): 629–635.
Article history
Received:
January 22 2001
Revision Received:
May 14 2001
Accepted:
July 18 2001
Citation
Sagar N. DOSHI, Katerina K. NAKA, Nicola PAYNE, Christopher J.H. JONES, Moira ASHTON, Malcolm J. LEWIS, Jonathan GOODFELLOW; Flow-mediated dilatation following wrist and upper arm occlusion in humans: the contribution of nitric oxide. Clin Sci (Lond) 1 December 2001; 101 (6): 629–635. doi: https://doi.org/10.1042/cs1010629
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