Effect of melatonin on melanoma cells subjected to UVA and UVB radiation in In vitro studies.

Studies performed in vivo and in vitro have shown that exogenous melatonin (Mel) exerts oncostatic effects on melanoma cells. Although the protective effect of Mel on skin and cells exposed mainly to UVB has been documented, effects of Mel have not yet been examined on melanoma cells exposed to UVA. Our investigations aimed at examination of the effect of Mel alone (0, 10(-3), 10(-6) and 10(-9) M), and after its addition to the culture medium for 30 minutes before exposure of melanoma cells to UVA (15 J/cm(2)) or UVB (30 mJ/cm(2), 60 mJ/cm(2)). Viability of the cells was examined using the colorimetric sulphorhodamine B test. Mel added to the medium at concentrations of 10(-3)-10(-8) M was found to increase the number of melanoma cells as compared to the control (cells with no Mel) after 24 hours. Compared to exposed cells without Mel, at 10(-3) M Mel, melanoma cells exposed to 30 mJ/cm(2) UVB increased in number and at 10(-9) M increased the survival of those exposed to 60 mJ/cm(2) UVB. The cells exposed to UVA (15 J/cm(2)) were protected by Mel at 10(-6) and 10(-9) M. Physiological concentrations of Mel exerted no oncostatic effects on the BM cell line used here. In addition, the pharmacological Mel concentrations stimulated proliferation of the cells. Beyond doubt, we have confirmed that Mel represents a substance which protects cells from UVA and UVB action in in vitro experiments.