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OXALATE DEPOSITION ON ASBESTOS BODIES
Citation:
Ghio, A., V. L. Roggli, J. Richards, J. Stonehuerner, AND C. A. Piantadosi. OXALATE DEPOSITION ON ASBESTOS BODIES. Presented at American Thoracic Society Annual Meeting, San Francisco, CA, May 18-23, 2001.
Description:
The clinical and histopathologic findings in three patients with a deposition of calcium oxalate crystals on ferruginous bodies after occupational exposure to asbestos are provided. In addition, we test the hypothesis that this oxalate can be generated through a nonenzymatic oxidation of ascorbate by iron associated with the asbestos body therefore accounting for the deposition of the crystal on a ferruginous body. Crocidolite asbestos (100 Fg/mL) was incubated with 500 FM H2O2 and 500 FM ascorbate for 24 hours at 22oC. A dependence of oxalate generation on iron-catalyzed oxidants was tested with the inclusion of 1000 FM of either the metal chelator deferoxamine or the radical scavenger dimethylthiourea. Lung tissue sections from the individual exposed to asbestos demonstrated birefringent crystals with a dipyramidal tetragonal habit. The crystals were deposited exclusively on either asbestos bodies or fragments of bodies and were insoluble in 5% acetic acid. Examination by scanning electron microscopy and dot mapping showed morphological features and elemental spectra consistent with calcium oxalate. The in vitro incubation of crocidolite with H2O2 and ascorbate for 24 hours generated approximately 42 nmoles oxalate. This generation was diminished by the inclusion of either deferoxamine or dimethylthiourea in the reaction mixture. We conclude that the nonenzymatic production of oxalate by iron associated with asbestos can account for the deposition of this crystal on a ferruginous body. This does not necessarily reflect EPA policy.