Ammonium chloride and L-tyrosine enhance melanogenesis in vitro but not in vivo even in combination with ultraviolet radiation.
OBJECTIVE
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.


CONCLUSIONS
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.
Kongshoj
Brian
B
Department of Dermatology, Bispebjerg Hospital, Copenhagen, Denmark. bm14@bbh.regionh.dk
Mikkelsen
Nikolaj Dam
ND
Kobayasi
Takasi
T
Lerche
Catharina Margrethe
CM
Wulf
Hans Christian
HC
D000643:Ammonium Chloride / Q000494:pharmacology*; D000818:Animals; D045744:Cell Line, Tumor; D005260:Female; D006801:Humans; D008543:Melanins / Q000096:biosynthesis*; D051379:Mice; D008812:Mice, Hairless; D008854:Microscopy, Electron; D014443:Tyrosine / Q000494:pharmacology*; D014466:Ultraviolet Rays