Effect of SNP on ODQ-dependent decrease of cAMP level of oxygenated and deoxygenated RBC from day 11. RBC suspensions were preequilibrated in air or 1% oxygen for 25 minutes before the addition of NE (10 μmol/L for 15 minutes) in the absence or presence of 100 μmol/L SNP; ODQ (30 μmol/L) was added after 10 minutes of preequilibration. Data are the mean values and SD from 4 experiments.