The Autoxidation of Human Red Cell Lipids Induced by Hydrogen Peroxide

Abstract

S ummary . Malonyldialdehyde (MDA) formation, a measure of polyunsaturated fat autoxidation, was estimated in normal human red cells incubated in vitro. Exposure to oxygen under a variety of conditions did not induce autoxidation. Exposure to hydrogen peroxide was either by the addition of a hydrogen peroxide solution or by incubation in an atmosphere saturated with hydrogen peroxide vapour. A pattern of MDA formation was established with both methods. Lack of reproducibility, a feature of previous methods of measuring the susceptibility of red cells to exogenous peroxide, could be overcome by (i) catalase inhibition, (ii) attention to the non‐linear relation between packed‐cell volume and MDA formation, and (iii) elimination of potentially misleading coloured complexes on spectroscopy. A number of recognized antioxidants inhibited peroxide‐induced MDA formation. Inhibition was proportional to the logarithm of the antioxidant concentration. Under certain conditions pre‐incubation with nucleosides and with lecithin protected the cells against autoxidation on subsequent exposure to peroxide. Peroxide‐induced cell autoxidation was also influenced by plasma, bovine albumin, and ascorbic acid. Haemolysis was an invariable consequence of autoxidation. Similarities and dissimilarities between autoxidation and antioxidation in free lipid emulsions and in organized biological structures were examined and discussed in the light of the experimental findings.