RBC MPs trigger vaso-occlusive crises in SAD mice. We injected 5 × 10³ (blue and brown) or 300 × 10³ RBC MPs/mouse (yellow) intravenously to wild-type (WT) or SAD transgenic mice. We monitored vaso-occlusion in kidneys by echo-Doppler recording of hemodynamic parameters in vivo. (A) We determined mean blood flow velocity (cm/s) in the right renal artery. Measures were acquired before (none), or after injection of WT or SAD RBC MPs (*P < .05 vs control, none; #P < .05 vs SAD RBC MPs [5 × 10³ MPs/mouse]; $P < .05 vs WT RBC MPs; †P < .05 vs SAD RBC MPs [300 × 10³ MPs/mouse]). In some experiments, SAD RBC MPs were pre-incubated with annexin-V before injection. (B) Representative echo-Doppler waveforms in the renal artery of SAD mice before and after injection of WT or SAD RBC MPs, with or without preincubation with annexin-V. We also determined the heart rate (C; beats per minutes) and calculated the cardiac output (D; mL/min) from recording in the pulmonary artery. (E) Histologic analysis of SAD kidneys 5 minutes after injection of SAD RBC MPs, alone or pre-incubated with annexin-V, by Masson trichrome staining. Green arrows show areas of vascular congestion and erythrocyte deposits.