Phototoxicity of exogenous protoporphyrin IX and delta-aminolevulinic acid in the photo hen's egg test

Photodermatology, Photoimmunology & Photomedicine
Norbert J NeumannP Lehmann

Abstract

Oxygen, appropriate light sources, and special photosensitizers are necessary to induce photochemical damage in tumor cells via photodynamic therapy (PDT) delta-aminolevulinic acid (ALA) is increasingly used in PDT, because topical or systemic administration of ALA induces accumulation of endogenous porphyrins preferentially in neoplastic tissues. Subsequent radiation with light of approximately 630 nm leads to selective damage of tumor cells. PDT should optimally leave peritumoral tissues unaffected, but only few data are reported on the effects and the time course of ALA-induced porphyrins in tumor-free tissues. Therefore, we studied the phototoxic effects of protoporphyrin IX (PP) and ALA-induced porphyrins in a recently established phototoxic model based on tumor-free tissue, the photo hen's egg test (PHET). Employing this test procedure, PP provoked strong phototoxic reactions when irradiated with Ultraviolet A immediately and up to 30 h after substance application. In contrast, ALA induced a significant phototoxic effect only if irradiated 24 h after application. Thus, we observed a delayed phototoxic effect of ALA in tumor-free tissue of the yolk sac (YS) blood vessel system. This delayed phototoxic response 24 h after A...Continue Reading

Citations

Jun 3, 2005·Biological & Pharmaceutical Bulletin·Constance Lay Lay SawPaul Wan Sia Heng

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