PROGRESSIVE EFFECTS OF PHLORHIZIN ON MELANOGENESIS IN B16 MOUSE MELANOMA-CELLS

When we studied the effects of polyphenols from apple fruits on melano genesis in B16 mouse melanoma cell lines, phloridzin had dose-dependen t progressive effects on melanogenesis between 10 and 500 mu g/ml with out inhibiting cell growth, At a concentration of 500 mu g/ml, phlorid zin increased the melanin content in the cells to 181% of that in cont rol cells. In contrast, phloretin, the aglycon of phloridzin, did not activate melanogenesis in the cells and was cytotoxic at a concentrati on of 5 mu g/ml. Phloridzin increased the activity of tyrosinase:to 22 3% of that in control cells. Furthermore, phloridzin inhibited the act ivity of protein kinase C (PKC), which is recognized to regulate tyros inase activity. The inhibition of PKC activity continued for 120 min f rom the addition of phloridzin. Therefore, we estimated that the activ ation of melanogenesis by phloridzin resulted from the increase of tyr osinase activity caused by the inhibition of PKC activity.