Systemic responsiveness to endothelium-dependent vasodilators was blunted in sickle mice and BM-S mice, showing mean ± SEM for 5 or 6 mice per group. (A) NO donor sodium nitroprusside (10 μg/kg intravenous bolus) had blunted systemic vasodilator response in sickle mice and BM-S mice compared with controls. Similar blunted responsiveness was observed at a lower dose (3 μg/kg intravenous bolus, P < .05, data not shown). (B) Sildenafil (30 μg/kg/min) had significantly blunted systemic vasodilatory responses in sickle mice and in BM-S mice compared with controls. (C) Bradykinin had blunted mean arterial pressure response in the sickle mice at 3 μg/kg intravenous bolus. Similar results were observed at lower doses for BM-S (0.3 and 1 μg/kg, P < .05 and <.05, respectively; data not shown). Mixed response was observed at lower doses for sickle mice (0.3 and 1 μg/kg, P = NS and P < .05, respectively; data not shown). (D) Response to another endothelium-dependent vasodilator, adrenomedullin (1 μg/kg intravenous bolus) was likewise blunted in sickle mice but not in BM-S mice. Neither type of mouse was significantly different from controls at a lower dose of adrenomedullin (0.3 μg/kg, P = NS, data not shown). Statistically significant results noted as follows: *P < .05 versus hemizygotes; #P < .05 compared with mice receiving transplants with wild-type marrow (BM-C).