| Abstract: | The slow reacting hemolytic lysolecithin analog 1-octadecyl-2-benzyl-glycero-3-phosphorylcholine has been employed for a detailed study of the process of lysolecithin induced hemolysis. Using a radiolabelled analog we found that the different sensitivities of red cells from different species (chicken, man, cattle) are not paralleled by the binding affinities of lysolecithin. Moreover, lysophosphatide binding to the cells is reduced at low temperatures while the hemolytic activity increases. In contrast to continuous changes of lytic activity and binding between 0 and 37 degrees C, the velocity of the hemolytic reaction with human erythrocytes is extraordinarily fast at 10 degrees C. Experiments in sucrose containing buffer indicated principally different lysis mechanisms below and above 15 degrees C. We have further shown that cells loaded sublytically with the lysolecithin at 37 degrees C undergo spontaneous lysis upon cooling to 0 degrees C. The degree of lysis under these conditions, however, is diminished with increasing amounts of cell-bound lysolipid. Determinations of membrane microviscosities by means of fluorescence polarization revealed some qualitative relations between membrane fluidity and sensitivity to lysolecithin. The data are discussed on the basis of recent reports indicating that lysolecithin-distribution in mixed lipid phases may be heterogeneous depending on lipid composition and temperature. |
