Membrane lipid peroxidation as a mechanism of sonodynamically induced erythrocyte lysis

Abstract

Sonodynamically induced lipid peroxidation with haematoporphyrin (Hp) was studied using rat erythrocytes. Both suspensions of erythrocyte ghosts and of intact erythrocytes were exposed to ultrasound in the same way in the presence and absence of Hp (80 muM). The lipid peroxidation in erythrocyte ghost membranes was estimated by measuring the amount of reactive substance produced from thiobarbituric acid added immediately after the exposure. Haematoporphyrin multiplied the ultrasonically induced lipid peroxidation by three to five times, while Hp alone showed no peroxidation. A 24-h interval between the exposure and the preparation for measurement did not increase the measured amount of peroxide. In the presence of Hp the estimated peroxidation rate and the rate of erythrocyte lysis correlated quite well for each acoustic condition and for each chemical condition such as the presence or absence of active oxygen scavengers in the suspension. The sonodynamically induced lipid peroxidation with Hp was doubled by deuterium oxide substitution for suspension medium and was significantly reduced by histidine, by sodium azide, and also by nitrogen substitution for saturation gas, whereas superoxide dismutase and mannitol showed no significant inhibitory effect. These results are consistent with a hypothesis that lipid peroxidation in membranes by singlet oxygen is the primary mechanism of sonodynamically induced erythrocyte lysis with Hp.