Accéder au contenu
Merck

Hypoxic potentiation of nitrite effects in human vessels and platelets.

Nitric oxide : biology and chemistry (2014-05-27)
Rustem F Dautov, Irene Stafford, Saifei Liu, Hugh Cullen, M Madhani, Yuliy Y Chirkov, John D Horowitz
RÉSUMÉ

Previous studies in non-human blood vessels and in platelets have demonstrated that under hypoxic conditions release of NO from nitrite (NO2(-)) is potentiated by deoxyhaemoglobin. In the current study, we characterized hypoxic potentiation of NO2(-) effects in human vasculature and platelets in vitro, addressing underlying mechanisms. The vasodilator efficacy of NO2(-), in comparison with glyceryl trinitrate (GTN), was evaluated in vitro, using segments of human saphenous vein. Under hypoxic conditions, there was a leftward shift of the NO2(-) concentration-response curve (EC50: 22 μM in hyperoxia vs 3.5 μM in hypoxia; p<0.01), but no significant potentiation of GTN effect. In the presence of red blood cells, hypoxic potentiation of NO2(-) vasodilator effect was accentuated. In whole blood samples and platelet-rich plasma (PRP) we assessed inhibition of platelet aggregation by NO2(-) (1mM), in comparison with that of sodium nitroprusside (SNP, 10 μM). In individual subjects (n=37), there was a strong correlation (r=0.75, p<0.0001) between anti-aggregatory effects of NO2(-) and SNP in whole blood, signifying that resultant sGC activation underlies biological effect and responses to NO2(-) are diminished in the presence of NO resistance. In PRP, the effects of NO2(-) were less pronounced than in whole blood (p=0.0001), suggesting an important role of Hb (within RBCs) in the bioconversion of NO2(-) to NO. Inhibition of platelet aggregation by NO2(-) was almost 3-fold greater in venous than in arterial blood (p<0.0001), and deoxyHb concentration directly correlated (r=0.69, p=0.013) with anti-aggregatory response. Incremental hypoxia applied to venous blood samples (in hypoxic chamber) caused a progressive increase in both deoxyHb level and anti-aggregatory effect of NO2(-). When subjects inhaled a 12% O2 mixture for 20 min, there was a 3-fold rise in blood deoxyHb fraction (p<0.01). In PRP, response to NO2(-) also increased under hypoxia, and was further enhanced (p<0.01) by deoxyHb. Furthermore, deoxyHb exerted significant anti-aggregatory effects even in the absence of added NO2(-), suggesting a role for endogenous NO2(-). The results of this work provide further mechanistic insights into hypoxic potentiation of vasodilator and anti-aggregatory actions of NO2(-). In human saphenous veins and blood, the balance of evidence suggests differential rates of NO release from NO2(-) (largely modulated by deoxyHb) as the fundamental mechanism.

MATÉRIAUX
Référence du produit
Marque
Description du produit

Sigma-Aldrich
Sodium nitrite, ReagentPlus®, ≥99.0%
Le tarif et la disponibilité ne sont pas disponibles actuellement.
Sigma-Aldrich
Sodium nitrite, ACS reagent, ≥97.0%
Le tarif et la disponibilité ne sont pas disponibles actuellement.
Sigma-Aldrich
Sodium nitrite, 99.999% trace metals basis
Le tarif et la disponibilité ne sont pas disponibles actuellement.
Sigma-Aldrich
Adenosine 5′-diphosphate, ≥95% (HPLC)
Le tarif et la disponibilité ne sont pas disponibles actuellement.
Supelco
Sodium Nitroprusside, Pharmaceutical Secondary Standard; Certified Reference Material
Le tarif et la disponibilité ne sont pas disponibles actuellement.
Supelco
Sodium nitrite, analytical standard
Le tarif et la disponibilité ne sont pas disponibles actuellement.
Supelco
Nitrite ion standard solution, 0.1 M NO2-, for ion-selective electrodes
Le tarif et la disponibilité ne sont pas disponibles actuellement.
Sigma-Aldrich
Sodium nitrite, anhydrous, Redi-Dri, ReagentPlus®, ≥99.0%
Le tarif et la disponibilité ne sont pas disponibles actuellement.