Influence of UVA and UVB on human melanocytes growth.

[Objective]To investigate the distinct response between human melanocytes separately exposed to UVA and UVB.[Methods]The proliferation rate of melanocytes was determined by MTT assay.The viability of intracellular tyrosinase was determined by photocolorimetry.The levels of intracellular melanin was evaluated by spectrophotometry.[Results]Human normal melanocytes irradiated with 0-2.25J/cm2 UVA showed no marked changes while high dose UVA(1.8J/cm2)caused an obvious drop in cell proliferation.0-0.06 J/cm2 UVB showed significant increase in melanin content and tyrosinase activity and a drop of cell proliferation in dose-effect manner.[Conclusion]In vitro,the melanotropin synthesis of melanocytes induced by UVB was obviously greater than that by UVA.