Impaired phagocytic ability of the retinal pigmented epithelial (RPE) cells and cellular swelling of the retina is a noted condition seen in disease states such as age related macular degeneration and retinitis pigmentosa. Phagocytosis involves the invagination of the cell membrane and the engulfment of particles; both of these processes require the cell to adaptively change volume. Changes in cell volume are facilitated by gradient-dependent fluid movement. This phenomenon can be observed during regulatory volume decreases (RVD) and regulatory volume increases (RVI), in which organic osmolytes move out of and into the cell respectively. Taurine, the most abundant organic osmolyte in the human body is present in high concentrations in the RPE cells. In this study, we examined a human RPE cell line, ARPE-19, and investigated its phagocytic activity under various osmotic conditions and various taurine culture conditions. An increase in the uptake of microspheres was observed in cells exposed to hypoosmotic medium (∼200mOsm) in comparison to cells exposed to normoosmotic medium (∼300mOsm). This increase was reduced when cells were concurrently exposed to guanidinoethyl sulfonate (GES), a taurine transporter inhibitor. No change in phagocytosis was seen in cells exposed to hyperosmotic medium (∼400mOsm). Interestingly, our intracellular taurine measurements under the various osmotic conditions did not have the expected values considering the RVD/RVI processes. Phagocytic activity was also increased through long term GES culturing, although long term high taurine culturing had no effect. This data supports the hypothesis that RVDs, through taurine movement, but not RVIs, can enhance phagocytic activity. These data also supports the hypothesis that cells with lower resting intracellular taurine levels result in smaller resting cell volumes and therefore have a greater ability to accommodate engulfed particles.
|School:||University of the Sciences in Philadelphia|
|School Location:||United States -- Pennsylvania|
|Source:||MAI 47/01M, Masters Abstracts International|
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