Pulmonary vascular effects of red blood cells containing S-nitrosated hemoglobin

S Deem, SS Kim, JH Min, R Eveland… - American Journal …, 2004 - journals.physiology.org
S Deem, SS Kim, JH Min, R Eveland, J Moulding, S Martyr, X Wang, ER Swenson…
American Journal of Physiology-Heart and Circulatory Physiology, 2004journals.physiology.org
The role of S-nitrosated hemoglobin (SNO-Hb) in the regulation of blood flow is a central
and controversial question in cardiopulmonary physiology. In the present study, we
investigate whether intact human red blood cells (RBCs) synthesized to contain high SNO-
Hb levels are able to export nitric oxide bioactivity and vasodilate the pulmonary circulation,
and whether SNO-Hb dependent vasodilation occurs secondary to an intrinsic oxygen-
linked, allosteric function of Hb. RBCs containing supraphysiological concentrations (100 …
The role of S-nitrosated hemoglobin (SNO-Hb) in the regulation of blood flow is a central and controversial question in cardiopulmonary physiology. In the present study, we investigate whether intact human red blood cells (RBCs) synthesized to contain high SNO-Hb levels are able to export nitric oxide bioactivity and vasodilate the pulmonary circulation, and whether SNO-Hb dependent vasodilation occurs secondary to an intrinsic oxygen-linked, allosteric function of Hb. RBCs containing supraphysiological concentrations (100–1,000× normal) of SNO-Hb (SNO-RBCs) were synthesized and added to isolated, perfused rat lungs during anoxic or normoxic ventilation, and during normoxic ventilation with pulmonary hypertension induced by the thromboxane mimetic U-46619. SNO-RBCs produced dose-dependent pulmonary vasodilation compared with control RBCs during conditions of both normoxic (U-46619) and hypoxic pulmonary vasoconstriction. These effects were associated with a simultaneous, rapid, and temperature-dependent loss of SNO from Hb. Both vasodilatory effects and the rate of SNO-Hb degradation were independent of oxygen tension and Hb oxygen saturation. Furthermore, these effects were not affected by inhibition of the RBC membrane band 3 protein (anion exchanger-1), a putative membrane facilitator of NO export from RBCs. Whereas these data support observations by multiple groups that synthesized SNO-Hb can vasodilate, this effect is not under intrinsic oxygen-dependent allosteric control, nor likely to be relevant in the pulmonary circulation at normal physiological concentrations.
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