MEMBRANE LIPID-PEROXIDATION AS A MECHANISM OF SONODYNAMICALLY INDUCEDERYTHROCYTE LYSIS

Sonodynamically induced lipid peroxidation with haematoporphyrin (Hp) was studied using rat erythrocytes. Both suspensions of erythrocyte gh osts and of intact erythrocytes were exposed to ultrasound in the same way in the presence and absence of Hp (80 mu M). The lipid peroxidati on in erythrocyte ghost membranes was estimated by measuring the amoun t of reactive substance produced from thiobarbituric acid added immedi ately after the exposure. Haematoporphyrin multiplied the ultrasonical ly induced lipid peroxidation by three to five times, while Hp alone s howed no peroxidation. A 24-h interval between the exposure and the pr eparation for measurement did not increase the measured amount of pero xide. In the presence of Hp the estimated peroxidation rate and the ra te of erythrocyte lysis correlated quite well for each acoustic condit ion and for each chemical condition such as the presence or absence of active oxygen scavengers in the suspension. The sonodynamically induc ed lipid peroxidation with Hp was doubled by deuterium oxide substitut ion 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 inhib itory effect. These results are consistent with a hypothesis that lipi d peroxidation in membranes by singlet oxygen is the primary mechanism of sonodynamically induced erythrocyte lysis with Hp.