Hemolysis induces platelet aggregation and mitochondrial dysfunction. (A-D) Platelet activation measured by surface p-selectin expression (A) or percent of activated glycoprotein IIb/IIIa (B), platelet aggregation 15 minutes after treatment (C), and complex V activity (D) in untreated (control) healthy platelets or those exposed to free hemoglobin or oligomycin (0.4 µmol/L) or ADP (20 µM, to stimulate aggregation). (E) Basal respiratory rate (solid line) and mitochondrial hyperpolarization (dashed line) in healthy platelets exposed to increasing concentrations of free hemoglobin. (F) H₂O₂ generation in hemoglobin-treated platelets (n = 5, *P < .01 vs untreated).