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. Author manuscript; available in PMC: 2014 Mar 1.
Published in final edited form as: Exp Dermatol. 2013 Mar;22(3):202–209. doi: 10.1111/exd.12099

Figure 2. The metabolic product of 9-cis retinal oxidation, 9-cis retinoic acid, acts to stimulate melanin accumulation.

Figure 2

(A) 9-cis retinal alone is sufficient to induce melanin accumulation. MNT-1 melanoma cells were briefly treated with the indicated doses of 9-cis retinal and then allowed to reach confluency. Melanin accumulation was measured as described in the methods section. (B) 9-cis retinoic acid potently stimulates melanin accumulation. MNT-1 melanoma cells were briefly treated with the indicated doses of 9-cis retinoic acid and allowed to reach confluency. Melanin accumulation was measured as described in the methods section (C) A light micrograph of a representative opaque-walled, clear-bottomed 96-well microtiter plate containing MNT-1 cells treated with 9-cis retinoic acid is shown. Med, wells containing only media; Veh, cells treated with vehicle. (D) All-trans retinoic acid does not appreciably induce melanin accumulation. MNT-1 melanoma cells were briefly treated with the indicated doses of all-trans retinoic acid and allowed to reach confluency. Melanin accumulation was measured as described in the methods section. Data shown are mean ± S.D. (n=6 as indicated by the error bars). *, p < 0.05 or **, p < 0.01 using a Student’s paired t-test with a two-tailed normal distribution versus vehicle-treated control.