Background: No comparative and simultaneous in vitro studies have been performed to determine the cytotoxic dose of narrowband UVB (NBUVB) and broadband UVB (BBUVB) for keratinocytes, melanocytes, and fibroblasts. Culture medium was often replaced with phosphate-buffered saline (PBS) before UV irradiation; however, its amount differed across studies. We determined the cytotoxic doses of NBUVB and BBUVB and tested for changes in viability according to the amount of PBS.
Methods: We exposed cultured human keratinocytes, melanocytes, and fibroblasts to ultraviolet light in the range 12.5-1000 mJ/cm(2) for NBUVB and 1.25-100 mJ/cm(2) for BBUVB. The viability was assessed after 24 h. We also determined changes in viability at cytotoxic doses according to the amount of PBS (40, 80, and 120 microl/well in a 96-well plate).
Results: Cytotoxicity was observed at doses of 100, 200, and 400 mJ/cm(2) for NBUVB and 5, 10, and 25 mJ/cm(2) for BBUVB in keratinocytes, melanocytes, and fibroblasts, respectively. At cytotoxic doses, there was no change in viability according to the amount of PBS.
Conclusions: Fibroblasts are more resistant to UVB irradiation, irrespective of the amount of NBUVB and BBUVB, than keratinocytes and melanocytes. The amount of PBS during irradiation had no effect on viability.