Proposal for a new UVA protection factor: use of an in vitro model of immediate pigment darkening.
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.
Routaboul
Corinne
C
Bioderma, 75, cours A.-Thomas, 69447 Lyon Cedex 3, France. routabou@chimie.ups-tlse.fr
Denis
Alain
A
Bohbot
Michel
M
D006801:Humans; D017495:Hyperpigmentation / Q000503:physiopathology*; D066298:In Vitro Techniques; D008544:Melanocytes / Q000187:drug effects / Q000528:radiation effects; D008962:Models, Theoretical; D010777:Photochemistry; D012680:Sensitivity and Specificity; D012878:Skin Neoplasms / Q000209:etiology / Q000517:prevention & control; D012880:Skin Pigmentation / Q000528:radiation effects*; D013473:Sunscreening Agents / Q000494:pharmacology*; D014466:Ultraviolet Rays / Q000009:adverse effects*
D013473:Sunscreening Agents