Figure 3.
Assessment of the role of MT1/MT2 receptors in terms of melatonin and its metabolites-mediated melanogenesis in human MNT-1 melanoma cells. Cells were pre-incubated for 2 h with a nonselective MT1 and MT2 receptor antagonist, that is, 10 μM luzindole or selective MT2 receptor antagonist, i.e., 0.1 μM 4-P-PDOT. Next, cells were treated for 72 h with 10−3 M MEL, AFMK, 5-MT or 6(OH)MEL and assessed for melanin content (A,B) and tyrosinase activity (C,D) as described in Materials and Methods. Data are presented as the mean + S.E.M. (n = 5) and values are normalized and expressed as percentage of the control value. Statistically significant differences are indicated as * p < 0.05, ** p < 0.01, *** p < 0.001.