EFFECTS OF UV-SENSITIZATION OF HEMATOPORPHYRIN ON LIPID HYDROPEROXIDES IN ERYTHROCYTES AND ON THEIR HEMOLYSIS

We have already reported the effect of ultraviolet-A (UVA)-sensitizati on of hematoporphyrin (HP) on the production of lipid hydroperoxides i n erythrocytes and on their hemolysis. In this report,we investigated these effects under ultraviolet-B (UVB) irradiation and compared the r esults with those under UVA irradiation. It was found that an increase in lipid hydroperoxide preceded hemolysis, and that the UVB irradiati on resulted in an increase in phosphatidylethanolamine hydroperoxide ( PEOOH) and 2-thiobarbituric acid reactive substances (TBA-RS) at an ea rlier stage in comparison with UVA irradiation. Under either UVA or UV B irradiation, hemolysis was inhibited by anti-oxidants such as sodium azide and ascorbic acid (singlet oxygen scavengers), but not by manni tol, sorbitol (hydroxyl radical scavengers) or superoxide disumutase ( SOD) (superoxide radical scavenger). These results suggest that single t oxygen (O-1(2)) produced by UV irradiation peroxidized the lipids of erythrocyte membranes, and therefore, the hemolysis of erythrocytes o ccured when the amount of hydroperoxides increased to a constant level , but auto-oxidation of lipids did not affect the hemolysis.