[Increased level of nitric oxide stable metabolites in the blood of highlanders]

The investigation was designed to study nitric oxide (NO) blood level estimated by measuring its stable metabolites nitrite (NO2-) and nitrate (NO3-) concentration in highlanders (2,200 m a.s.l.). NO2- [symbol: see text] NO3- concentration was measured with Griss reagent and brucine reagent respectively with using the spectrophotometric method. We first found that highlanders compared to lowlanders have increased blood level of NO2- (37 +/- 3.3 nmol/ml vs. 28.5 +/- 1.3 nmol/ml, P < 0.05) and NO3- (1362 +/- 43 nmol/ml vs. 845 +/- 65 nmol/ml, P < 0.001). As the most significant, there was increase in NO2- concentration in erythrocytes (by about 6 times), NO3- level in erythrocytes was revealed to be increased by 2.5 times, whereas the plasma concentration of these stable metabolites was the same (for NO3-) or even slightly decreased (for NO2-). Such increased NO stable metabolites blood level in highlanders may explain widening of vasodilative reserve and strengthening of cardiac pump and contractile functions, which we revealed previously. Activation of NO-system in high altitude is important and probable trigger adaptive mechanism of cardiovascular system to hypoxia. This mechanism allows to retain adequate tissue perfusion and optimal oxygen supply in its decreased partial pressure in inhaled air and thereby to prevent diseases caused by vasospastic processes.