Spectrin-haemoglobin crosslinkages associated with in vitro oxidant hypersensitivity in pathologic and artificially dehydrated red cells

S ummary . Protein crosslinkages are apparent at 215000–250000 daltons in electrophoregrams of membranes from hydrogen peroxide treated erythrocytes (British Journal of Haematology , 48 ,435, 1981). Hydrogen peroxide is also capable of inducing crosslinkages of identical molecular weights in stage I and II (red) ghosts and in a mixture of purified spectrin and haemoglobin, but not in white ghosts or in either spectrin or haemoglobin alone. Autoradiographic studies using ¹⁴C-methae-moglobin and ³²P-spectrin confirm the involvement of spectrin and haemoglobin in this reaction. The alpha chains of both proteins are more reactive than the corresponding beta chains: 3 times more reactive in the case of spectrin and 10 times more reactive in haemoglobin. The reaction is almost totally inhibited by NaCN and partially inhibited by N-ethylmaleimide. Direct addition of malondialdehyde to a spectrin-haemoglobin mixture does not result in protein crosslinkage. Metabolic depletion (40 h), in vivo ageing and sucrose dehydration of fresh, normal cells enhance the reaction considerably, whereas in vitro rehydration of xerocytes normalizes their H₂O₂ sensitivity.