Nitric oxide transport in blood: A third gas in the respiratory cycle

Allan Doctor, Jonathan S. Stamler

Research output: Contribution to journalArticlepeer-review

61 Scopus citations


The trapping, processing, and delivery of nitric oxide (NO) bioactivity by red blood cells (RBCs) have emerged as a conserved mechanism through which regional blood flow is linked to biochemical cues of perfusion sufficiency. We present here an expanded paradigm for the human respiratory cycle based on the coordinated transport of three gases: NO, O2, and CO2. By linking O2 and NO flux, RBCs couple vessel caliber (and thus blood flow) to O2 availability in the lung and to O2 need in the periphery. The elements required for regulated O2-based signal transduction via controlled NO processing within RBCs are presented herein, including Snitrosothiol (SNO) synthesis by hemoglobin and O2-regulated delivery of NO bioactivity (capture, activation, and delivery of NO groups at sites remote from NO synthesis by NO synthase). The role of NO transport in the respiratory cycle at molecular, microcirculatory, and system levels is reviewed. We elucidate the mechanism through which regulated NO transport in blood supports O2 homeostasis, not only through adaptive regulation of regional systemic blood flow but also by optimizing ventilation-perfusion matching in the lung. Furthermore, we discuss the role of NO transport in the central control of breathing and in baroreceptor control of blood pressure, which subserve O2 supply to tissue. Additionally, malfunctions of this transport and signaling system that are implicated in a wide array of human pathophysiologies are described. Understanding the (dys)function of NO processing in blood is a prerequisite for the development of novel therapies that target the vasoactive capacities of RBCs.

Original languageEnglish
Pages (from-to)541-568
Number of pages28
JournalComprehensive Physiology
Issue number1
StatePublished - Jan 2011


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