Photochemical damage to skin fibroblasts caused by protoporphyrin and violet light.

Foreskin fibroblasts cultured in a medium containing protoporphyrin and exposed to violet light lose the capacity to proliferate. This phenomenon can be assessed on the basis of the ability of the irradiated cells to form colonies. Potentially lethal injuries can, however, be repaired during postirradiation incubation under optimal growth conditions. We investigated the photodynamically induced transformations of certain molecular targets in the irradiated cells. Biochemical analysis showed that only traces of unsaturated fatty acids were oxidized, but SH groups of both the membranes and the cytosol appeared to be very sensitive targets. Of the tryptophan content, 20% was damaged during irradiation. Recovery was observed during post-irradiation incubation. The tryptophan content and the SH groups recovered to some extent, and these results showed a good correlation with the regeneration of surviving cells.