Role of iron in the generation of radicals by freshly fractured silica: augmentation of pulmonary reactions to silica inhalation.
Castranova-V; Vallyathan-V; Ramsey-DM; Pretty-JR; Pack-D; Leonard-S; Barger-MW; Ma-JYC; Teass-AW
Toxicologist 1996 Mar; 30(1)(Part 2):272
Fracturing quartz produces radicals on the fracture planes and generates hydroxyl radicals (OH) in aqueous media. OH production is directly associated with silica-induced cell damage and phagocyte activation in vitro. This OH production in vitro is inhibited by desferol, an iron chelator. The present objective was to determine if iron increased the ability of inhaled silica to cause inftammation and lung injury. Male Fischer rats were exposed 5 hrs/day for 10 days to filtered air, 20 mg/m3 freshly milled silica (30-40 ppm iron) or 20 mg/m3 freshly milled silica doped with iron (>500 ppm iron). High iron silica produced approximately 70% more radicals in vitro than the low iron silica. Compared to inhalation of low iron silica, high iron silica resulted in greater neutrophil recruitment (^ 900%), macrophage production of oxygen radicals measured by electron spin resonance or chemiluminescence (132% or 90%, respectively), nitric oxide production by macrophages (^71%), and lipid peroxidation of lung tissue (^38%). The results suggest that inhalation of a mixture of iron and freshly fractured silica may be more pathogenic than inhalation of silica alone.
Silicates; Silica-dusts; Quartz-dust; Cell-damage; In-vitro-study; In-vitro-studies; Lung-disorders; Pulmonary-system-disorders; Pulmonary-disorders; Laboratory-animals; Animals; Animal-studies; Exposure-levels; Exposure-assessment; Lung-tissue; Inhalation-studies
HELD; DRDS; DBBS
The Toxicologist. Society of Toxicology 35th Annual Meeting, March 10-14,1996, Anaheim, California