Vasorelaxant effects of RBC S-nitrosothiols. (A) SNO-RBCs were synthesized and contained elevated concentrations of SNO (inset). Addition of these cells to aortic rings precontracted with phenylephrine (PE; 100 nM) and L-NMMA (100 μM) stimulated dilation (indicated by a decrease in tension). (B) Representative vessel tension versus time traces showing that RBCs isolated from LPS-treated rats (black line) stimulate vasorelaxation at 0.003 and 0.01 (0.3% and 1%) hematocrit, whereas control RBCs (gray line) have no effect. (C) Dose-dependent relaxation stimulated by LPS RBCs (black) relative to control RBCs (gray). Data represent mean ± SEM (n = 5). *P ≤ .05 versus control.