Effect of nitric oxide and nitric oxide donors on red blood cell oxygen transport

A mechanism has been proposed in which nitric oxide (NO) may bind to cysteine beta 93 and be transported B haemoglobin from the lungs to the tissues and modify vascular tone. In addition, it has been reported that treatment of sickle cell anaemia blood with 80 p.p.m. NO gas in air shifts the oxygen affinity as measured by P-50 to the left. We exposed normal and sickle cell anaemia blood to 80 p.p.m. NO in air for 1 h in vitro and found no change in P-50 of either normal or sickle cell blood, in addition, we exposed normal and sickle cell blood in buffer to aqueous NO (NO gas dissolved in buffer) at varying concentrations and found that the induced left shift in P-50 correlates strongly and linearly with methaemoglobin formation. We also treated normal and sickle cell blood with other nitric oxide donors, such as sodium 2-(N,N-diethylamino)-diazenolate-2-oxide (DEANO), S-nitrosocysteine (CysNO) and sodium trioxodinitrate (OXINO, or Angeli's salt). In all cases, we found a dose-dependent increase in methaemoglobin that was strongly correlated with the dose-dependent P-50 reduction. Our data do not support the report that low NO concentrations call selectively increase the oxygen affinity of sickle fell blood without affecting methaemoglobin levels significantly. NO, however map have benefit in sickle cell disease by other mechanisms.