Soluble haemoglobin-induced rheological impairment: A role for oxygen free radical formation

It has been demonstrated that iron and iron compounds facilitate hydroxyl radical generation from activated oxygen species. Free haemoglobin (Hb), like other iron-rich substances, might also mediate hydroxyl radical production and induce lipid peroxidation and cell damage. On the basis of the hypothesis that Hb may influence circulating blood cells, namely red cells, studies have been carried out on the effect of Hb on rheological properties of whole blood. Hb is capable of significantly influencing whole blood filterability and, to a lesser extent, whole blood viscosity. The addition of Fe2+ has a potentiating effect; superoxide dismutase and thiourea which are respectively selective inhibitors of superoxide anion and hydroxyl radicals are able to antagonize the Hb-induced rheological impairment. From these observations, the hypothesis may suggest that Hb negatively influences some rheological properties of whole blood by producing oxygen free radicals. Hb released in vivo at the site of arterial stenosis and of atherosclerotic plaque rupture may induce a rheological impairment and, so doing, play a role in microcirculatory derangement. © 1991 Pergamon Press plc.