A SIMPLE FLUORESCENCE METHOD FOR THE STUDY OF THE INTERNALIZATION OF PARTICLES IN CULTURED-CELLS - APPLICATION TO ASBESTOS AND GLASS-FIBERS

A model for the study of internalization of particles in mammalian cel ls was applied to asbestos and glass fibres. Briefly, a fluorescent fl uid-phase endocytic marker, Lucifer Yellow CH (LY), was allowed to be incorporated into the lysosomal compartment of Syrian hamster embryo c ells. Mineral fibres that were internalized by the cells subsequently became 'fluorescent', presumably when the fibre-containing endosome fu sed with the LY-containing lysosomes. This method was compared with di fferential interference contrast (DIC) optics. Approximately three tim es as many of the cell-associated fibres were determined to be interna lized by the fluorescence method compared with DIC optics. Both fine a nd coarse glass fibres were internalized as effectively as asbestos fi bres. The relative frequency of internalized (i.e. fluorescent) fibres increased until 4 hr after exposure compared with the total number of cell-associated fibres. The frequency of internalized fibres compared with the number of cell-associated fibres was constant over the range of fibre levels studied. A surface modification (octadecyldimethylchl orosilane-derivatization) of amosite fibres that decreased the carcino genicity of the fibres, decreased slightly the number of internalized fibres relative to the number of cell-associated fibres, but this was not statistically significant. Cytoskeleton-interfering agents signifi cantly decreased the relative number of internalized fibres.