Chemiluminescence and Biologic Reactivity of Freshly Fractured Silica.
Dalal-NS; Vallyathan-V; Leelarasamee-N; Castranova-V; Dyke-K
NIOSH 1990 Nov:943-946
The chemiluminescence and biological reactivity of freshly fractured silica (14808607) were examined. The chemiluminescence of freshly ground silica or silica that had been aged for up to 48 hours in air or HEPES buffered medium was monitored for several days. Freshly ground silica was added to HEPES buffered medium containing 125 micrograms per milliliter (microg/ml) superoxide-dismutase (SOD) or catalase or 100 millimolar 5,5-dimethyl-1-pyrroline-1-oxide (DMPO) to assess the effects of these free radical scavengers on silica chemiluminescence. Alveolar macrophages obtained by lavage from male Sprague-Dawley-rats were incubated with 20microg/ml freshly ground silica or silica that had been aged for 24 or 48 hours. Lucigenin stimulated chemiluminescence was monitored. Freshly ground silica emitted substantially more light than aged silica both in air and in HEPES buffer. The chemiluminescence intensity of freshly ground silica decreased with time, showing a halflife of approximately 40 minutes. SOD, catalase, and DMPO inhibited light emission by freshly ground silica by 71, 88, and 97%, respectively. Alveolar macrophages generated lucigenin dependent chemiluminescence that peaked 8 minutes after exposure to silica. The magnitude of the response was significantly greater in macrophages that had been treated with freshly ground silica than those exposed to aged silica. The authors suggest that cleavage of silica can produce excited surface sites that can react with aqueous media to form reactive oxygen species which emit light. The chemiluminescence of freshly fractured silica probably results from the deexcitation of these radicals. Alveolar macrophages exposed to freshly ground silica generate excessive amounts of reactive species. This implies that oxidative stress may be an etiological factor in acute silicosis.
NIOSH-Author; Silica-dusts; Surface-properties; Luminescence; In-vitro-studies; Alveolar-cells; Free-radicals; Oxidative-processes; Mammalian-cells;
Proceedings of the VIIth International Pneumoconioses Conference