Osmotic properties of human erythrocytes treated by phospholipase A2 from bee venom

During treatment of human red cells with phospholipase A2 from bee venom, a linear increase of the MCV and of the osmotic fragility occurs in parallel with the cleavage of the accessible phospholipids. However, even after maximal hydrolysis, i.e. degradation of up to 65% of the phosphatidylcholines and up to 6% of the phosphatidyl-ethanolamines, almost no haemolysis is observed and the median corpuscular fragility is only 7% higher than that of control cells incubated without enzyme. Addition of albumin to the medium results in an important rise of the susceptibility to hypotonic saline solutions. Osmotic fragility curves obtained with red cells submitted to mild phospholipase action show evidence of subpopulations of cells with various sensitivities to osmotic lysis. This phenomenon can be partly explained by the heterogeneity of the cleavage intensity among the cell population. This hypothesis is supported by the studies of the lipid composition of phospholipase treated red cells fractionated according to their sensitivity to hypotonic lysis or to their size.