Lysosome destruction and lipoperoxide formation due to active oxygen generated from haematoporphyrin and UV irradiation.

The lysosomal enzymes, acid-phosphatase and beta-glucuronidase, were released from rat liver lysosome when exposed to 400 nm irradiation in the presence of haematoporphyrin, and the release was prevented by adding vitamin E, diazabicyclo-octane, bovine serum albumin, superoxide dismutase or D-mannitol to the reaction mixture. Monochromatic irradiation with wavelengths from 380 to 410 nm caused no significant differences in the release of lysosomal enzymes, but 420 nm irradiation caused three-fifths of that of 400 nm irradiation. The malondialdehyde level in rat liver homogenate increased after 400 nm irradiation in the presence of haematoporphyrin. Reduction of nitroblue-tetrazolium was not observed when haematoporphyrin was excited by 400 nm; it was considered that superoxide anion radical (O2--) was not primarily generated. The following mechanism was assumed: that porphyrin which had been excited by 400 nm, converted ground-state molecular oxygen (3O2) to excited singlet oxygen (1O2), which formed lipid peroxides in lysosomal membrane resulting in destruction of the membrane; skin changes would occur from these released lysosomal enzymes.