THE EFFECT OF FIBER LENGTH ON THE DISSOLUTION BY MACROPHAGES OF ROCKWOOL AND GLASSWOOL FIBERS

The effect of fiber length on the dissolution of experimental rockwool and commercial glasswool fibers in rat alveolar macrophage (AM) cultu re and in mere culture medium was studied. The ultrastructure of macro phages after their exposure to fibers and the suitability of macrophag e-type cell line P388D1 culture in dissolution studies were also explo red, The fiber samples included short (ground) and long (untreated) ro ckwool and glasswool fibers. The fibers were incubated in rat AM cultu res, in P388D1 culture, or in mere culture medium for 4 or 8 days. The dissolution of the fibers was determined by measuring the amounts of silicon (Si), iron (Fe), and aluminum (Al) in the medium. There were n o differences in the diameter of the fibers, but a clear difference ex isted in the length of the short and long fibers. The dissolution of S i, Fe, and Al was more pronounced from experimental rockwool than from commercial glasswool fibers. The dissolution of Si was always greater in mere culture medium than in rat AM culture. Moreover, the dissolut ion of Si was greater from the long fibers than from the short ones. O n the contrary, the dissolution of Pe and Al in AM culture exceeded th at in mere culture medium. The dissolution of Si, Fe, and Al from both fibers in P388D1 culture was similar to their dissolution in rat AM c ulture. The fibers were also effectively phagocytized by the macrophag es, The present results together suggest that the intracellular and th e extracellular dissolutions of man-made vitreous fibers differ from e ach other. (C) 1995 Academic Press, Inc.