MUTAGENICITY OF 8-METHOXYPSORALEN AND LONG-WAVE ULTRAVIOLET-IRRADIATION IN V-79 CHINESE-HAMSTER CELLS - 1ST APPROACH TO A RISK ESTIMATE IN PHOTOCHEMOTHERAPY

The effect of 8-methoxypsoralen (8-MOP) and long-wave ultraviolet irradiation (UVA) on cell killing and mutation induction was studied in V-79 Chinese hamster cells. No effect was observed after treatment with 8-MOP alone (50 μg/ml, 4 h), UVA alone (9000 J/m2), or 8-MOP metabolized by rat-livermicrosomes. Combined treatment with 8-MOP and UVA induced both cell killing and mutation. This was also observed under conditions approaching patient treatment with PUVA photochemotherapy with respect to the concentration of 8-MOP in the skin and the amount of UVA received by the epidermal cells. A simple relation proved to apply for mutation induction under different treatment conditions: 5.5 × 10-8 per J/m2 per μg 8-MOP/ml. On this basis the mutation induction in dividing cells per session of PUVA-photochemotherapy amounts to 12.4 × 10-5, which is probably an over-estimation. © 1979.