RESUMEN
BACKGROUND: The stratom corneum lipids, responsible for the epidermal water bar rier, consist mainly of ceramides, cholesterol and free fatty acids. However, little has been studied about the effects of non-polar, polar and mixed organic solvents on the changes of the stratum corneum lipids bilayer. OBJECTIVE: We designed this study in order to investigate the effect of non-polar, polar and mixed organic solvents on the lipids bilayer in hairless mice. METHODS: Twenty four hairless mice were evenly divided into 4 groups; a control group, chloroform treated group, methanol treated group and mixed solvent(chloroform/methanol(2:1) ) treated gr oup. The changes in transepidermal water loss, as measured with an evaporimeter, were recorded after topical application of either chloroform, methanol or mixed solvents at 0, 3, 6, 12, 24 and 48 hours respectiveh. For electron microscopy, the skin samples taken from the mice of ea.:h group were t.rented with osmium tetroxide and ruthenium tetroxide after the treatment with each solvent. RESULTS: The results were as follows ; 1. From 0 to 24 hours after treatment with each solvent transepidermal water loss was significantly increased in the chloroform and the mixed solvent[chloroform/methanol(2:1)] treated groups, compared to the methanol treated group and control group(P<0.001). 2. 48 hours after treatment with each solvent, the differences in the values of transepidermal water loss in all groups were insignificant. 3. On electronmicroscopic examination, separation of intercellular lipid bilayers and a decrease in the numher of lamellar bodies were more severe in the chloroform treated and mixed solvent (chloroform/methanol(2:1)] treated groups than in the methanol treated group. Application of non-polar organic solvents, especially mixed solvents[chloroform/methanol(2:1)] resulted in an increase in transepidermal water loss and greater structural changes than with polar organic solvents. CONCLUSION: Our results suggest that non-polar lipids may play a more important role in the protection of water vaporization of the stratum corneum lipids barrier than polar lipids.