PREFERENTIAL RELATIVE PORPHYRIN ENRICHMENT IN SOLAR KERATOSES UPON TOPICAL APPLICATION OF DELTA-AMINOLEVULINIC-ACID METHYLESTER

Topically applied delta-aminolevulinic acid is used efficiently for th e treatment of solar keratoses by photodynamic therapy, Recent animal studies suggest that porphyrin sensitization of epithelial tissue is i mproved by using esters rather than free delta-aminolevulinic acid. Th e present study examines porphyrin metabolite formation after topical application of delta-aminolevulinic acid or delta-aminolevulinic acid methylester in human solar keratoses versus adjacent normal skin, Leve ls of total porphyrins, porphyrin metabolites and protein were measure d in skin samples excised after 1 and 6 h. Higher levels of porphyrins were observed in solar keratoses than in normal skin with both substa nces, Maximum porphyrin levels were present in solar keratoses treated with delta-aminolevulinic acid for 6 Ih. However, the ratio of porphy rins in solar keratoses versus adjacent normal skin was higher with de lta-aminolevulinic acid methylester. The pattern of porphyrins showed no significant difference between normal and afflicted skin, protoporp hyrin being predominant. The results suggest that application of free delta-aminolevulinic acid may be more effective in sensitizing solar k eratoses, However, treatment with delta-aminolevulinic acid methyleste r leads to a preferential enrichment of porphyrins within lesional ski n.