Abstract: The purpose of this study is to invest the effect of arotinoid ethylester (Ro13-6298) on ultraviolet B(UVB)-induced melanogenesis of human normal melanocytes (HNM) and provide experimental evidence for treating pigmented diseases of skin. HNM taken from 6 normal persons cultured in vitro were treated with 100mJ/cm²/day and/or different concentrations (10^-9～10^-5mol/L) of Ro13-6298 respectively, Ro13-6298 were added immediately after each irradiation. 2, 4 and 6 days after the irradiation, tyrosinase activity was estimated by measuring the rate of oxidation of L-DOPA, and melanin content by the value of optical density absorbance of NaOH treated HNM. Results showed that tyrosinase activity and melanin content of treated HNM after 4-day-UVB irradiation increased significantly (P<0.05～0.01) than those of non-irradiated cells, but there was no statistical difference between the non irradiated cell group and Ro13-6298 treatment group. Little effect was found on the melanin synthesis in the non-irradiated HNM treated with Ro13-6298 (10^-9～10^-5). Conclusion: the melanogenesis of cultured HNM can be induced by repeated small dose of UVB irradiations through increasing tyrosinase activity, Ro13-6298 can inhibit melanogenesis induced by UVB irradiation on HNM at lower concentration in vitro.

Key words: Retinoids, Ultraviolet ray, Melanocytes