Contrasting respirable quartz and kaolin retention of lecithin surfactant and expression of membranolytic activity following phospholipase A2 digestion.
Wallace-WE; Keane-MJ; Mike-PS; Hill-CA; Vallyathan-V; Regad-ED
J Toxicol Environ Health 1992 Nov; 37(3):391-409
The rates of digestive removal of dipalmitoyl-lecithin (DPL), a component of pulmonary surfactant, by phospholipase-A2 (PLA2) and recovery of membranolytic activity for a quartz (14808607) and a kaolin (1332587) dust were compared. Stock dispersion of DPL in physiologic saline was generated by sonication. Dry silica or kaolin mineral dusts were vortexed into emulsions of DPL/saline. DPL treated kaolin and quartz were incubated with PLA2 for periods of 2 to 72 hours at different applied enzyme concentrations. The hemolytic potentials of the mineral dusts were determined by an erythrocyte hemolytic assay. A rapid loss of adsorbed DPL in the first 2 hours of incubation with PLA2 was observed for both quartz and kaolin dusts. This was followed by a slower loss of the remaining DPL. The rate of DPL removal increased with increasing applied concentrations of enzyme for incubation times greater than 2 hours. DPL removal rates were greater for quartz bound than for kaolin bound DPL. The hemolytic activity of treated quartz was greater than the native quartz activity for all three enzyme levels at 2 and 22 hours, and treated quartz activity roughly equaled that of native quartz at 44 and 72 hours. The hemolytic activity of treated kaolin was greater than the native kaolin activity at 2 hours. Significantly decreased hemolytic activities for digestion times greater than 2 hours for the two lower enzyme levels were observed in DPL coated kaolin.
NIOSH-Author; Comparative-toxicology; Hemolysis; Mineral-dusts; Phospholipids; Plasma-membrane; Pulmonary-system; Respirable-dust; Silica-dusts; Surfactants; Toxic-effects
Journal of Toxicology and Environmental Health