The formation of
reactive oxygen species resulting from the interaction of
silica dust particles with red blood cell membranes was investigated; particularly, the effect of surface
hydroxyl (
silanol) group concentration on the rate of formation of such
reactive oxygen species was investigated. The rate of formation was measured indirectly through the effect of
catalase, a hemoprotein
peroxidase, on
silica-induced
hemolysis. It was found that the addition of exogenous
catalase to erythrocytes markedly reduces the
hemolysis caused by
silica particles. Furthermore, the amount of
catalase required for deactivation of
silica per unit area of particle surface is lower for fumed
silica particles and calcined crystalline particles than for uncalcined, crystalline
silica, suggesting a correlation between the concentration of
OH groups at the
silica particle surface and its potential for generation of H2O2. The addition of
albumin, a
copper chelator, also decreases
hemolysis. These results suggest that the
hemolysis caused by
silica particles is at least partly related to the formation of H2O2 at the particle surface and its subsequent reaction with Cu+
ions. The relationship between the concentration of surface
silanol groups on the
silica surface and the amount of
catalase required to decrease
hemolysis may also provide a method for testing potential fibrogenicity of respirable dusts.