Hemoglobin (Hb) in intact erythrocytes exists both in soluble and membrane-bound states. Hemoglobin transition to the membrane-bound state (MBHb) can be physiologically significant. We can presume that it provokes an adaptive reaction aimed to change different parameters connected with erythrocyte biochemistry and membrane properties. Nitric oxide (NO) is known to affect hb-membrane binding. We have shown that the addition of NaNO₂, сysNO and GSNO to the suspension of erythrocytes results in changes in MBHb concentration. hemolytic stability depends on MBhb level: even small MBHb
fluctuations change the level of erythrocytes hemolysis. NaNO2 triggered the highestbamplitude of MBHb changes due to the formation of free-radical products in the system (oxyHb − NaNO₂). Methylglyoxal (MG) provoked a dose-dependent increase of MBHb, whereas the Hb oxidative-reductive state was not affected. The level of MBhb was negatively correlated with the amount of reduced Sh-groups of membrane proteins. The addition of NO metabolites to erythrocytes suspension in the presence of MG induced various effects: NaNO
2 reduced MBhb by 50 %, сysNO by 20 %, while GS-NO, on the contrary,
slightly promoted the MBHb level. The effect of nitrosothiols can be explained by freeradical products being formed in the system (MG−Nh₃−Pr−RSNO), which promote Hb binding with membrane components by inducing lipid and protein oxidation processes. It was shown that even insignificant MBHb fluctuations resulted in changes of erythrocyte hemolysis rates.