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(Circulation Research. 2004;94:e105.)
© 2004 American Heart Association, Inc.

Letters to the Editor

How Do Red Blood Cells Dilate Blood Vessels?

Barry W. Allen

Department of Anesthesiology and Center for Hyperbaric Medicine and Environmental Physiology, Duke University Medical Center, Durham, North Carolina, barry.w.allen@duke.edu

Claude A. Piantadosi

Departments of Medicine and Anesthesiology and Center for Hyperbaric Medicine and Environmental Physiology, Duke University Medical Center, Durham, North Carolina

An extract of the first 250 words of the full text is provided, because this article has no abstract.

To the Editor:

Recently in this journal, a report by James et al¹ was paired with an editorial by Gladwin and Schechter.² However, the invited commentators did not discuss the novel finding of James et al that hemoglobin (Hb) glycosylation in diabetes impairs vasorelaxation by altering nitric oxide (NO) binding to Hb thiols. Instead, the guest editors focused on vascular dilation by red blood cells (RBCs) in the absence of disease, for which they now state that there are "two competing mechanisms." This imposes an unnecessary dichotomy on our emerging understanding of how RBCs dilate blood vessels with NO, as in hypoxic dilation. If the two alternatives in a dichotomy are not the sole alternatives, or are not mutually exclusive, or if neither is true, the dichotomy is false and forces sincere dissenters into extreme points of view, allows the dichotomists to frame the debate improperly, and wastes intellectual resources. All this impedes scientific advance.

This dialectic has a history. Last year, Gladwin et al wrote that experimental data and theoretical considerations "compellingly show" that RBCs do not dilate blood vessels through export of NO bioactivity.³ Then, Nagababu et al⁴ reported that deoxyHb reduces nitrite to NO in vitro and proposed that this accounts for local vasodilation, but did not claim it as the only such mechanism. Shortly thereafter, Cosby et al described in vivo studies from which they drew a similar conclusion and further asserted that nitrite (which produces NO bound to heme), "rather than" NO bound to Hb . . . [Full Text of this Article]

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