Myoglobin protects against endothelial cell membrane damage associated with hydrogen peroxide or xanthine/xanthine oxidase.

Oxymyoglobin at 'physiological' concentrations of 20-100 micromolar protected cultured endothelial cells from damage by xanthine/xanthine oxidase or by hydrogen peroxide. Metmyoglobin also provided a degree of protection, but apomyoglobin was ineffective. Protection was enhanced in the presence of ascorbate (0.01-1 mM). Myoglobin may have a physiological role in the protection of muscular tissue from ischaemia/reperfusion-induced damage.