Heme arginate–conditioned and hematin–conditioned LDL.

Heme arginate–conditioned LDL induced less endothelial cell lysis than hematin–conditioned LDL. Human umbilical vein endothelial cells were incubated with LDL (200 μg/mL protein) treated with hematin (5 μmol/L) plus H₂O₂ (75 μmol/L), LDL treated with heme arginate (HA) (5 μmol/L) plus H₂O₂, and LDL treated with H₂O₂ alone in HBSS for 4 hours. Endothelial cells were also exposed to native LDL alone, and for control cells, HBSS was free of lipoprotein. Results were the percentage of specific cytotoxicity (mean ± SE) of 3 experiments performed in duplicate. P < .004 versus LDL treated with hematin plus H₂O₂.