A novel model for testing enhancers of pigmentation

Mouse skin, unlike human skin, does not contain active epidermal melanocytes, with the exception of the ear and tail skin in some pigmented strains. We have investigated enhancement of pigmentation in inbred C3H- mice using tail skin as a model for testing the effects of phosphorylated DOPA (DP) and ultraviolet radiation. Mice were restrained by cage dividers and treated with various doses of DP in dimethylsulphoxide (DMSO) or DMSO alone with or without the addition of UV radiation. Each tail served as its own control since only the dorsal surface was treated and irradiated. Pigmentation was graded blindly on histologic sections stained with Fontana-Masson. UV radiation caused a marked increase in epidermal and dermal pigmentation and this was enhanced in a dose-dependent manner by DP. However, there was minimal effect from DP alone.