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 Printable version |
Proposal for a new UVA protection factor: use of an in vitro model of immediate pigment darkening |
European Journal of Dermatology. Volume 12, Number 5, 439-44, September - October 2002, Rapports d'investigature
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 Free Article
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Author(s) : Corinne ROUTABOUL, Alain DENIS, Michel BOHBOT |
Summary : In order to define a new method for measuring UVA photoprotection, we built an in vitro immediate pigment darkening model (IPD). IPD is a photochemical reversible reaction induced by UVA on the skin. Our model consists of aqueous solutions of melanocytic compounds (dihydroxyphenylalanine/pheomelanins). Irradiation of these solutions with UVA induces an increase in their absorbance. Oxygen deprivation inhibits the solution darkening and light turn-off induces a decrease in the absorbance as observed in vivo.
A UVA photoprotection parameter (Puva) was defined using the ability of a sunscreen to inhibit the model reaction. A calibration of the reaction inhibition is realised using neutral beam attenuators. Puva is defined as the percentage absorbance of a beam attenuator which would have the same inhibitory effect as the sunscreen tested. A correlation between Puva and Diffey-Robson parameter is presented. The method developed here could be use as a indicative tool before human experiments. |
Keywords : dihydroxyphenylalanine, immediate pigment darkening, melanin, protecting factors, ultraviolet A. |
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