2009 年 55 巻 2 号 p. 314-318
We examined the effect of δ-tocotrienol on melanin content in mouse melanoma B16 cells. Melanin content was significantly reduced in cells treated with 50 and 100 μM δ-tocotrienol, but not 10 μM δ-tocotrienol. The activity and amount of tyrosinase also significantly decreased in cells treated with 10, 50, and 100 μM δ-tocotrienol. Furthermore, the mRNA level of tyrosinase as measured using realtime PCR was significantly decreased compared to controls in cells treated with 100 μM δ-tocotrienol, but not 10 or 50 μM δ-tocotrienol. These results indicated that at first δ-tocotrienol caused tyrosinase degradation, and then caused a further decrease in the tyrosinase protein level via both tyrosinase degradation and a decrease in the mRNA level of tyrosinase. We conclude that the decrease of melanin content in the cells by δ-tocotrienol was the result of the decrease of the protein level of tyrosinase (tyrosinase degradation is more important than the decrease of mRNA).