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J Appl Physiol 99: 1620, 2005; doi:10.1152/japplphysiol.00864.2005
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POINT-COUNTERPOINT COMMENTS

Flow-mediated dilation

Beth A. Parker and David N. Proctor

Noll Laboratory
Department of Kinesiology
The Pennsylvania State University

ABSTRACT

This letter is in response to the Point:Counterpoint series "Flow-mediated dilation does/does not reflect nitric oxide-mediated endothelial function" that appeared in the September issue (vol. 99: 1233–1238, 2005; doi:10.1152/japplphysiol.00601.2005; http://jap.physiology.org/content/vol99/issue3/2005).

Authors Tschakovsky and Pyke (2) summarize flow-mediated dilation (FMD) in their rebuttal to Dr. Green as being nitric oxide (NO) dependent when the technique is 1) brachial or radial artery specific, 2) restricted to 5 min of distal cuff occlusion, and 3) in healthy subjects. Condition number three, however, is deserving of further clarification. To date, sex differences in the contribution of NO to 5 min of distal occlusion have not been well classified. The majority of studies referenced by Tschakovsky and Pyke and/or Green involving intra-arterial infusions of NO-synthase inhibitors have been conducted in men; those studies involving women have generally involved an overall sample size or female population too small to detect sex differences between subjects. Given that Levenson et al. (3) found that women exhibit a greater brachial artery dilation per unit increase in shear rate after 5 min of distal (forearm) occlusion and that estrogen may modulate both relaxing (PGI2, NO, endothelium-derived hyperpolarizing factor) and constricting (thromboxane, endothelin) substances released from the vascular endothelium (4), it is possible that the mechanisms underlying FMD in women differ from those established in men. Furthermore, although an age-associated decline in brachial artery FMD resulting from 5 min of distal occlusion has been well-documented in healthy humans (1), it is unknown whether this decline represents diminished NO-dependent dilation, as the mechanisms underlying FMD have not been thoroughly characterized in older adults and may involve additional endothelial pathways. Thus we would remind readers that both sex and age may influence the NO dependence of brachial or radial artery FMD.

REFERENCES

  1. Celermajer DS, Sorensen KE, Spiegelhalter DJ, Georgakopoulos D, Robinson J, and Deanfield JE. Aging is associated with endothelial dysfunction in healthy men years before the age-related decline in women. J Am Coll Cardiol 24: 471–476, 1994.[Abstract]
  2. Green G; Tschakovsky ME and Pyke KE. Point:Counterpoint: Flow-mediated dilation does/does not reflect nitric oxide-mediated endothelial function. J Appl Physiol 99: 1233–1238, 2005.[Free Full Text]
  3. Levenson J, Pessana F, Gariepy J, Armentano R, and Simon A. Gender differences in wall shear-mediated brachial artery vasoconstriction and vasodilation. J Am Coll Cardiol 38: 1668–1674, 2001.[Abstract/Free Full Text]
  4. Orshal JM and Khalil RA. Gender, sex hormones, and vascular tone. Am J Physiol Regul Integr Comp Physiol 286: R233–R249, 2004.[Abstract/Free Full Text]



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B. N. Torgrimson, J. R. Meendering, C. T. Minson, B. Geny, O. Rouyer, S. Doutreleau, and F. Piquard
Commentary on Point-Counterpoint
J Appl Physiol, January 1, 2006; 100(1): 362 - 362.
[Full Text] [PDF]

This Article
Right arrow Abstract Freely available
Right arrow Full Text (PDF) Free
Right arrow Submit a response
Right arrow Alert me when this article is cited
Right arrow Alert me when eLetters are posted
Right arrow Alert me if a correction is posted
Right arrow Citation Map
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Web of Science (1)
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Parker, B. A.
Right arrow Articles by Proctor, D. N.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Parker, B. A.
Right arrow Articles by Proctor, D. N.

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