Skin permeation and distribution of two sunscreens: a comparison between reconstituted human skin and hairless rat skin

The aims of this work were (a) to develop a simple and reproducible procedure for percutaneous absorption and distribution tests of sunscreens using one human skin culture model (Epiderm TM 606; reconstructed epidermis, RE), (b) to compare the said model with rat skin (RS) in vitro and (c) to evaluate the effect of different formulations. The cutaneous permeation and distribution of two UV filters, ethylhexylmethoxycinnamate (MC80) and ethylhexyltriazone (T150), using 3 different vehicles were investigated. The permeation studies demonstrated that neither MC80 nor T150 permeated through both RS and RE in spite of different thicknesses of the 2 substrates. Distribution studies demonstrated that sectioning by cryomicrotome to obtain horizontal skin layers was suitable for both RS and RE (apart from its small thickness) with a good reproducibility of data. The amounts of sunscreens retained in the 2 substrates were in the same order of magnitude for all formulations with a greater depot in RS. Different distribution profiles of the tested formulations could be ascribed to the different lipid compositions of RE and RS. Since the physicochemical characteristics of RE arecloser to those of human skin, the results obtained with reconstructed human skin models could be suitable to replace human skin in ‘in vitro testing’.