Fig. 4. Effects of nitric oxide (NO) on oxygen affinity of erythrocytes. Exposure to NO (80 ppm for 15 min) shifted the oxygen dissociation curve of hemoglobin S erythrocytes to the left ( left ). The effect of NO exposure on P50of hemoglobin S erythrocytes was dose-dependent ( right ). Values are mean ± SE. Reprinted with permission from Head et al. 12 by copyright permission of The American Society for Clinical Investigation.