Hydroxyl radical generating activity of hydrous but not calcined kaolin is prevented by surface modification with dipalmitoyl lecithin.
Baser-ME; Kennedy-TP; Dodson-R; Rao-NV; Rawlings-W Jr.; Hoidal-JR
J Toxicol Environ Health 1990 Jan; 29(1):99-108
The effect of surface modification with dipalmitoyl-lecithin (DPL) on the radical generating activity of hydrous and calcined kaolin (1332587) was determined in a chemical system that measured hydroxyl radicals ((-)OH) as the evolution of methane (CH4) from dimethyl- sulfoxide (67685) (DMSO). Both hydrous and calcined kaolin exhibited marked activity as catalysts for producing (-)OH from hydrogen-peroxide (H2O2). In the presence of a reducing agent and 10 millimolar H2O2, hydrous and calcined kaolin generated mean CH4 concentrations of 1634 and 1395 parts per million (ppm), respectively. Surface modification with DPL, the lipid of pulmonary surfactant, blocked generation of (-)OH in hydrous kaolin (38ppm CH4) but not in calcined kaolin (875ppm CH4). Catalytic activity was prevented by preincubating kaolin with deferoxamine. The authors conclude that the catalytic activity of kaolin for producing (-)OH from H2O2 may be important in the pathogenesis of kaolin toxicity. Calcined kaolin may be more toxic than hydrous kaolin because the calcined form is resistant to surface modification by lipids of pulmonary surfactant.
NIOSH-Author; Toxicology; Aluminum-compounds; Free-radical-generation; Chemical-reactions; Chemical-properties; Toxic-materials; Lung-disorders; Lung-irritants
Journal of Toxicology and Environmental Health
University of Tenn Center Health Scien, Memphis, Tennessee