Mouse hepatoma cells, mitochondria, and lysosomes of rat liver cells after incubation with hematoporphyrin derivative (HPD) were treated by ascorbate and exposed to light. The product of membrane lipid peroxidation -- malondialdehyde (MDA) -- was determined. The MDA level increased with the increase of ascorbate content (in a range of certain concentrations) and irradiation time. Thiourea, an inhibitor of hydroxyl free radical, showed an inhibiting effect to the production of MDA in the experimental groups. The MDA level decreased with the increase of thiourea concentration. Ear index, a parameter to evaluate photosensitive reaction of mouse skin by HPD plus light was determined. The value of ear index of mice treated with ascorbate was greater than that of mice without ascorbate treatment. Those results suggest that hydroxyl free radical produced by HPD and ascorbate after light irradiation could oxidize membrane lipids, and showed that ascorbate may enhance porphyrin photosensitization of tumor cells.
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