Induction of multinucleate cells by 8-MOP and UV treatment in vitro and in vivo.

Fibroblast cells were treated with a single dose of 8-methoxypsoralen (8-MOP) and long-wave UV irradiation in vitro and the cytotoxic effects of the treatment followed up for 5 passages. During the first passage, there was an inhibition in cell proliferation, the induction of chromosomal aberrations and the production of macrocells as well as cells with more than one nucleus. In the subsequent passages, the proliferation rate of the cells gradually normalized but there was a concomitant increase in chromosomal aberrations and in the number of macrocells and multinucleate cells. Specimens, which were taken from the uninvolved skin of psoriatic patients who had been treated between 20 and 40 times with an oral dose of 8-MOP and black light irradiation (PUVA) also revealed the presence of binucleate, tetranucleate and multinucleate epidermal cells as well as binucleate and tetranucleate dermal fibroblasts.