Differential cytotoxic, growth-inhibiting and lipid-peroxidative activities of four different asbestos fibres in vitro

Abstract

An attempt was made to characterize the carcinogenic hazard of asbestos fibres by using a set of in vitro screening tests. The fibres tested were the serpentine chrysotile and the three amphiboles anthophyllite, crocidolite and amosite. Their cytotoxic and cytostatic activities in rat primary fibroblast-like cells were assessed along with their effects on enzymic lipid peroxidation by liver homogenates. After 24 hr exposure of fibroblast-like cells to 2.1 μg fibres/cm 2, chrysotile induced the highest cytotoxicity, followed by crocidolite, anthophyllite and amosite. Similarly, after 48 hr exposure, chrysotile had the most growth inhibiting effect, followed by crocidolite, anthophyllite and amosite. Enzymic lipid peroxidation, as measured by pentane or malondialdehyde production, was determined at ambient (21% O 2) or tissue (4% O 2) oxygen tension in incubation mixtures containing rat-liver homogenate and asbestos fibres. At 4% O 2, only the two iron-containing fibres, crocidolite and amosite, stimulated lipid peroxidation. The results suggest that the cytotoxic activity is influenced by the surface charge, structure and dimensions of the fibres, and that cell-growth inhibition is associated with surface charge, structure and the Mg 2+ content of the fibres. Effects on enzymic lipid peroxidation appear to be associated with the structure and iron content of the tested fibres. When these results are considered along with epidemiological data, it seems that the carcinogenic potency of asbestos fibres is characterized by an ability to induce high levels of enzymic lipid peroxidation along with moderate cytotoxic and growth inhibiting activities.