Alloxan-induced alterations in composition and dynamics of red blood cell membranes. I. Effect of alloxan on intact red blood cells and isolated erythrocyte membranes.

Changes of dynamics and chemical composition in membranes of intact red blood cells and isolated erythrocyte membranes treated with alloxan were investigated in order to assess whether alloxan-induced generation of active forms of oxygen may be critical for erythrocyte destroying. In vitro incubation of native red blood cells or prepared erythrocyte membrane ghosts with various concentrations of alloxan gave rise both to levels of membrane TBA-reacting substance and lipid membrane microviscosity both in the deeper and surface regions of lipid bilayer, as evidenced by fluorescence polarization technique. The amount of membrane phospholipid decreased upon alloxan action and that of membrane cholesterol remained rather unchangeable, thus resulting in significant elevation of membrane cholesterol:phospholipid (C:PL) ratio. Both time course and concentration effect of alloxan were found to change exponentially with the different rates of the reaction. There was a linear correlation between 1,6-diphenylhexatriene-1,3,5 (DPH) and 1-anilinonaphthalene-8-sulfonate (ANS) anisotropy coefficients and C:PL ratio (respectively r = 0.697 and r = 0.580) as well as TBARS levels (r = 0.386 for rDPH and r = 0.324 for rANS), thus implying the possible effect of membrane dialdehydes on bilayer components immobilization. Regression coefficients significance testing showed reaction rates of TBARS and C:PL changes to be significantly parallel, contrary to those of fluorescence anisotropy coefficients assessing considerably slower dynamics of alloxan-induced changes. The relevance of changes induced by alloxan in isolated erythrocyte ghosts and intact red blood cells and the compatibility of the present results with several previous studies support the widespreading idea pointing the cell membrane as a main target of damage during alloxan action.