Experimental induction of fibrogenesis by a nonmetallic acicular mineral particle was evaluated in-vitro. Rabbit alveolar macrophages were obtained by tracheal lavage. Initial mean cell volume, viability, oxygen consumption, and enzyme activities of the freshly harvested cells were determined prior to culturing of the cells. Macrophages were suspended in medium and incubated at 37 degrees-C, 80 percent humidity, and 5 percent carbon-dioxide (CO2). Unattached cells were discarded after 3 hours. Fresh medium and known concentrations of chrysotile (1332214), wollastonite (13983170), or polystyrene (9003058) latex beads were added to adherent macrophages. Aliquots of cells and media were taken at intervals of 1, 2, and 3 days. Macrophages were removed from flasks with cold buffer and gentle agitation. They were washed and the measurements were made. To measure cellular enzyme activities, aliquots of macrophages were taken up on a buffered solution, sonicated, and centrifuged. Clear supernatant lysate was used to determine cellular enzymatic activity for cytosolic lactic-acid- dehydrogenase, lysosomal glucuronidase, acetylglucosaminidase, galactosidase, and acid-phosphatase. Exposure of macrophages to chrysotile asbestos, wollastonite, or polystyrene latex beads had no significant effect on mean cell volume or oxygen consumption. Membrane integrity and cellular and extracellular quantities of cytosolic and lysosomal enzymes were not affected by either wollastonite or polystyrene latex beads. Treatment of macrophages with as little as 25 micrograms per milliliter (microg/ml) asbestos for 1 day decreased membrane integrity and caused release of cytosolic and lysosomal enzymes into the extracellular environment. Exposure to 250microg/ml of either wollastonite or polystyrene latex beads did not alter membrane integrity or extracellular enzyme quantities. The authors conclude that exposure to chrysotile asbestos at concentrations used does not kill macrophages. Asbestos does cause membrane weakness as a result of a decrease in ability of macrophages to exclude trypan-blue dye.
NIOSH, Document Report No. 147OL, 21 pages, 25 references