PHAGOSOMAL PH AND GLASS-FIBER DISSOLUTION IN CULTURED NASAL EPITHELIAL-CELLS AND ALVEOLAR MACROPHAGES - A PRELIMINARY-STUDY

The dissolution rate of glass fibers has been shown to be pH sensitive using in vitro lung fluid simulant models. The current study investig ated whether there is a difference in phagosomal pH (ppH)] between rat alveolar macrophages (AM) and rat nasal epithelia[ cells (RNEC) and w hether such a difference would influence the dissolution of glass fibe rs. The ppH was measured in cultured AM and RNEC using flow cytometric , fluorescence-emission rationing techniques with fluorescein-labeled, amorphous silica particles. Glass fiber dissolution was determined in AM and RNEC cultured for 3 weeks with fast dissolving glass fibers IG F-AI or slow dissolving ones (GF-B). The mean diameters of GF-A were 2 .7 mu m and of GF-B, 2.6 mu m, the average length of both fibers was a pproximately 22 to 25 mu m. Dissolution was monitored by measuring the length and diameter of intracellular fibers and estimating the volume , assuming a cylindrical morphology. The ppH of AM was 5.2 to 5.8, and the ppH of RNEC was 7.0 to 7.5. The GF-A dissolved more slowly in RNE C than in AM, and no dissolution was evident in either cell type with GF-B. The Volume loss with GF-A after a 3-week culture with AM was 66% compared to 45% for cultured RNEC. These results are different from t hose obtained using in vi?ro lung fluid-simulant models where dissolut ion is faster at higher pH. This difference suggests that dissolution rates of glass fibers in AM should not be applied to the dissolution o f fibers in epithelial cells.