Porphyrin-induced photodamage to isolated epidermal cells from hairless mice.

UVA light photodamages epidermal cells, as measured by inhibition of enzymatic activity and inhibition of respiration. This photodamage is greatly augmented in the presence of protoporphyrin as a photosensitizer. The increase in photodamage is greater for the cytosolic and mitochondrial enzymes lactate dehydrogenase and glutamate dehydrogenase and least for the lysosomal enzymes beta-glucuroninidase and N-acetyl-beta-glucosaminidase. Upon irradiation in the presence of protoporphyrin, N-acetyl-beta-glucosaminidase is released from the epidermal cells. These results may help to explain some features of the pathogenesis of erythropoietic protoporphyria.