IV PEO+ results in intravascular hemolysis, declines platelet count and the appearance of schistocytes in the peripheral blood accompanied by increased LMW VWF multimers. (A) The plasma PEO concentration of all PEO+ treated groups over time. Multidosed (5 times [5×]) guinea pigs were injected repeatedly with PEO+ at 1.5-hour intervals (as designated on x-axis). (B-E) Hematologic changes in cell free plasma hemoglobin, total RBC hemoglobin, hematocrit, and platelet count in guinea pigs after a single (1×) or repeated (5×) injections of 0.1 and 0.3 mg/kg PEO+. The inset in panel B provides a visualization of the extent of plasma hemoglobin in maximally dosed guinea pigs vs control. (F) Appearance of schistocytes (arrowheads) in blood smears prepared from PEO+ treated animals (modifed Wright-Giemsa stain; scale bar, 20 μm). Quantification of schistocytes in the peripheral blood 24 hours postinjection is presented as number per high power field. (G) The molecular weight distribution of VWF multimers in PEO+ treated guinea pig plasma samples was assessed by low-resolution (0.6%) SDS agarose gel electrophoresis at baseline (BL), 8 hours (T₈) and 24 hours (T₂₄) after injection. Platelet lysate (Pt) prepared from normal guinea pig blood was used as a reference for minimally proteolyzed HMW VWF. (H) VWF antigen and VWF collagen-binding activity in plasma collected at 8 and 24 hours after injection with PEO+. All data displayed as mean values ± SEM (n = 4 per group). Ag, antigen; CBA, collagen-binding activity; Ctrl, control; Hb, hemoglobin; HPF, high powered field; LMW, low-molecular-weight.