The role of oxygen in the photodamaging effect on erythrocytes of some photoallergic and phototoxic compounds.

Red blood cells irradiated with longwave ultraviolet light in the presence of a number of photoallergic or phototoxic compounds showed a marked loss of K+ ions. This process was strongly restricted by anaerobic conditions. During irradiation, oxygen was consumed. Since pre-irradiated photosensitizers were not toxic to erythrocytes, it is concluded that during irradiation, oxidative processes take place in the erythrocyte. The concentrations of the investigated photoallergic compounds required to induce photohaemolysis, were several times higher than those required for the phototoxic compound protoporphyrin. These findings indicate that photoallergic compounds, like the photodynamic compounds, also have photo-oxidative capacities, but to a much lower degree.