Erythrocyte osmotic fragility test as the measure of defence against free radicals in rabbits of different age.

Peroxidation of the unsaturated bonds of membrane lipids increases fragility and cellular lysis of red blood cells. Erythrocyte susceptibility to the free radicals (peroxyl radicals) generated in vitro by 2,2'-azo-bis(2-amidinopropane) hydrochloride (AAPH) was evaluated and expressed as 50% maximal haemolysis time (HT50) in 3 groups of rabbits of different age. Erythrocytes of 1.5-month-old rabbits were more sensitive to free radicals than those of 3.5- and 6-month-old ones. In the three groups, significant negative correlation (r = -0.8 to -0.98) between the lipid peroxidation rate (thiobarbituric acid reactive substances; TBARS concentration) in blood plasma and the erythrocyte resistance to free radicals was found. This result suggests that the plasma antioxidant defence system is interrelated with that of the red blood cells and that the erythrocytes can be a good model for studies of oxidative stress. The simple haemolysis test reflecting the free radical defence can be useful for evaluating the antioxidant properties of various compounds.