[Mechanism of cell damage by hematoporphyrin derivatives (HPD) plus light--I. Photooxidation of hepatoma cell membrane by HPD plus light].

Ascitic hepatoma cells of mice were incubated with three HPD. After the cell-bound HPD was treated by visible light, the product of membrane lipid peroxidation--malondialdehyde (MDA) was determined. The results showed that the MDA level increased with HPD concentration and exposure time, but it was unchanged in the control. Beta-carotene, a quencher of singlet oxygen, could inhibit the lipid photooxidation of the membrane of cell-bound HPD resulting in a decrease of MDA level which decreased with increase of beta-carotene concentration. Adding vitamin E in vitro and vivo, formation of the product of membrane lipid peroxidation of cell-bound HPD by light was inhibited and the MDA level decreased with the increase of vitamin E concentration. These results show that the singlet oxygen, produced by HPD bound cells following light activation, reacts directly with the polyunsaturated fatty acids on cell membrane to produce lipid peroxides leading to cellular damage.