Species differences in the susceptibility of erythrocytes exposed to free radicals in vitro

The susceptibility of human, cow, pig, sheep and rabbit erythrocytes to free radicals (peroxyl radicals) generated in vitro by 2,2'-azo-bis(2-amidinopropane) hydrochloride (AAPH) was evaluated by means of a haemolysis test and expressed as the time to 50% of maximal haemolysis (HT50). The most sensitive to damage by free radicals appeared to be the erythrocytes of pigs and sheep, their HT50 values being (mean +/- SEM) 85.1 +/- 1.28 min and 89.0 +/- 1.31 min, respectively. Human erythrocytes and those of cows and rabbits were about twice as resistant, their HT50 values being (mean SEM) 174.3 +/- 1.53 min, 181.2 +/- 1.22 min and 183.4 +/- 2.54 min, respectively. Pig and sheep erythrocytes used in the haemolysis test provided an indication of the antioxidant status in a shorter time (2.5 h versus 4.5 h) than those of the other species studied. The results indicate that the HT50 test may be a convenient alternative to the osmotic resistance test for defining the antioxidant resistance of erythrocytes.