Formation of a clastogenic factor by asbestos-treated rat pleural mesothelial cells.

The data of the present study indicate that chrysotile induces the formation of a clastogenic factor (CF) when mesothelial cells are exposed to these fibers in vitro. Ultrafiltrates of culture media induce chromosome damage in human lymphocytes used as a test system for the detection of clastogenic activity in conditioned media. According to the cut off of the filters (10,000 dalton), CF is a small molecule. Its exact nature is unknown. The intermediacy of active oxygen species in CF formation is suggested by the anticlastogenic effect of antioxidant enzymes such as superoxide dismutase and catalase. The data are similar to those obtained with other membrane-active agents, in particular the tumor promoter tetra-decanoylphorbol acetate (TPA). The model of membrane-mediated chromosome damage with CF formation is proposed for asbestos-induced cell injury.