Differential responses of rat alveolar and peritoneal macrophages to man-made vitreous fibers in vitro

Different approaches, including inhalation and intraperitoneal injection as says, have been used to assess the potential health effects of man-made vit reous fibers (MMVF), The purpose of this study was to compare the phagocyti c activity and the formation of reactive oxygen species by rat alveolar mac rophages (AM) and peritoneal macrophages (PM) upon exposure to MMVF10 glass wool and MMVF21 rock wool fibers. Macrophage (Me) (phi) phagocytosis of mi neral fibers was assessed by optical videomicroscopy and computer-aided ima ge analysis. M phi were classified as cells not associated with fibers, cel ls with attached fibers, cells with incompletely phagocytized fibers (an ap pearance known as "frustrated phagocytosis"), and cells with completely pha gocytized fibers. The production of superoxide anions by AM and PM upon inc ubation with MMVF10 and MMVF21 fibers was determined by the superoxide dism utase-inhibitable reduction of ferricytochrome C, PM were found to have a l ower phagocytic activity than AM. A significantly higher percentage of AM t han of PM underwent frustrated phagocytosis of MMVF10 and MMVF21 fibers. In line with these findings, AM generated higher levels of oxygen radicals th an PM upon exposure to MMVFS1 fibers. In contrast, MMVF10 fibers failed to induce the generation of reactive oxygen species by both AM and PM. Our in vitro results show that the phagocytic activity, in particular the frustrat ed phagocytosis of mineral fibers, was significantly lower in PM than in AM , The data support the idea that the durability and biopersistence of miner al fibers are higher in the peritoneal cavity than in the lung. (C) 2001 Ac ademic Press.