Fig. 4.

Appearance of NO in the headspace of sealed containers after injection of sodium nitrite (final concentration 0.5 mM) into PBS (☐, n = 5), human red blood cell suspensions (●, n = 3), and sheep red blood cell suspensions (○, n = 3). The heme concentration in the cell suspensions was ∼0.32 mM, and the pO₂ ∼30 Torr. NO analyzer (NOA) values were normalized to average 0 mV over the baseline period. Nitrite injection at t = 0 min resulted in a measurable increase in the release of NO from sheep (P = 0.005) and human (P = 0.008) cell suspensions (1-way ANOVA with Bonferroni correction), but there was no significant difference between human and sheep blood (2-way ANOVA). Mean values are ± SE.