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Bovine (BAM) and rat (RAM) alveolar macrophages were incubated in vitro with DQ12 quartz or UICC chrysotile asbestos either alone or in the presence ofdipalmitoyl lecithin (DPL). The reaction of the cells of both species to the untreated dust particles w similar quaHtatively and quantitatively, withalos ofviabibt and releaseof lacate and N-acetyl-3l-glucosaminidase after 20 hr ofincubation. In the presence ofDPL, the toxicity ofquartz to BAM disappeared completely, whereas the protective influence of the phospholipid was distinctly diminished in the case of RAM.The presence oflavage fluid waslss effective tban that of pure DPL. There was no e of DPL with asbestos either for BAM or for RAM. The effects of phagocytizable, suspended quartz particles were compared with the effects ofthe same type of particles fixed on a glass surface to exclude the possibility ofphagocytosis. The effect ofthe suspended particles on the viability and release of enzymes was more pronounced than that of the fixed particles On the other hand, superoxide anion production was stimulated to a much higher degree by the frmed quartz particles. This could be explabned by the continuingcontactofthe outer cell membrne with the silica surfes, whereas free partidles were rapidly phagocytized. The release oflysosomal enzymes induced by fixed quartz particles was a secondary phenomenon following cell death.

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Spherical and irregularly shaped mixed (U,Pu) oxide particles were administered to rats by inhalation and by intratracheal instillation. The lung retention of the particles was independent of particle shape and of the route of administration. Only a small percentage of the administered radioactivity was found in other organs. Detailed electron microscopic studies showed particles within membrane-enclosed vacuoles as well as lying free in the cytoplasm.