WHAT IS THE RELATIONSHIP BETWEEN HEMOLYTIC POTENTIAL AND FIBROGENICITY OF MINERAL DUSTS

The hemolytic reaction to a dust is often used as a potential indicato r of fibrogenicity of silicon dioxide polymorphs. However, occasionall y the hemolytic response may not correlate with the observed fibrotic response in vivo. For example, amorphous silicas are very hemolytic bu t have little or no fibrogenic activity. In our study, heat treatment was used to alter alpha-cristobalite, a known fibrogenic dust, to a mo re hydrophobic surface. Comparisons were made between heated and unhea ted alpha-cristobalite for hemolytic activity in vitro and for lung re sponse in vivo. Heat treatment resulted in decreased hemolytic respons e, but no change in the fibrotic response occurred in vivo. In additio n, the heat treatment resulted in increased initial dust accumulation, reduced short-term clearance, and enhanced long-term clearance in viv o. Increased inflammatory cell recruitment was also observed in lungs of animals exposed to alpha-cristobalite. Thus, whereas heat-induced s urface changes in alpha-cristobalite markedly altered the hemolytic ac tivity of the particles, no changes were observed in the fibrotic resp onse.