The aim of the present study was to investigate the role of nitric oxide (NO) in the regulation of hemoglobin oxygen affinity (HOA) in the presence of different oxygen partial pressure. In this research the effect of NO donors on gas-transport, acid-base balance, HOA indexes, metHb, iron-nitrosylhemoglobin amounts, and total nitrite/nitrate concentration was estimated in vitro. Experimentally, positive correlation was found between NO-dependent shift of HOA and hemoglobin oxygen saturation level. In conclusion, NO is a component of autonomous intraerythrocytic system of HOA regulation, which action is determined by oxygen in the blood. We assume that the physiological significance of such NO action is to maintain aerobic metabolism through optimal blood oxygenation in the pulmonary circulation, on the one hand, and, on the other hand, its compensation under low oxygen tension in the working tissues.
