Kongshoj B, Mikkelsen ND, Kobayasi T, Lerche CM, Wulf HC.
Photodermatology, photoimmunology & photomedicine · 2007
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Abstract
Background/purpose Melanogenesis can be induced in vitro in melanoma cells and melanocytes by adding substances able to neutralize intracellular acidic organelles like melanosomes. Further addition of l-tyrosine enhances the melanogenesis by increasing the tyrosinase activity. As such, the property of tyrosine as a pigmentation enhancer is used in promoting creams containing tyrosine. The objective of this study was to investigate whether such an effect could actually be seen in a short term in vivo mouse study. Methods Lightly pigmented C3.Cg/TifBomTac hairless mice capable of pigmenting had ammonium chloride (NH4Cl) and/or l-tyrosine applied topically (1/day for 3 weeks). Pigmentation of the mice was determined using the Kodak Gray Scale at days 0, 7, 14, and 21. Results Both NH4Cl and l-tyrosine yielded no significant effect, either alone or in combination, when applied using either hydrogel or moisturizing cream. Exposing mice to simulated solar radiation (4 standard erythema doses, 3/week) yielded increased pigmentation. However, no statistically significant difference was found between treatment with simulated solar radiation alone or in combination with NH4Cl and l-tyrosine. Conclusion In spite of the commercial value of adding l-tyrosine to 'pigmentation-enhancing' creams, topically applied l-tyrosine showed no pigmentation-enhancing effect, neither alone nor in combination with ultraviolet (UV) radiation, providing a basis to contest such promotional measures.