Changes in volume of peritoneal mesothelial cells exposed to osmotic stress

Objective: To evaluate changes in volume of mesothelial cells exposed to hy pertonic medium and the role of volume regulatory mechanisms in adaptation to hyperosmolality. Design: Experiments were performed on primary cultures of human peritoneal mesothelial cells. Cell volume was estimated by measuring equilibrated (int racellular/extracellular space) C-14-urea in cellular water. Cells in monol ayers were exposed to hyperosmotic media and changes in cellular water or i ntracellular uptake of H-3-proline were measured. Results: Exposure of mesothelial cell monolayers to hyperosmotic media redu ced the cell volume; the effect was proportional to the osmolality of the m edium. Volume of cells exposed to medium supplemented with glucose (180 mmo l/L) decreased by 26%, p < 0.001, after 30 minutes' incubation. Prolonged e xposure of mesothelial cells to hyperosmotic medium resulted in gradual rec overy, after initial decline, of their volume, Intracellular uptake of amin o acid 3H-proline increased after 240 minutes' exposure of the mesothelial cells to medium supplemented with glucose (90 mmol/L) (+40%, p < 0.05). Whe n cells cultured for 7 days in medium supplemented with glucose (45 mmol/L) were exposed to medium with low glucose content (5 mmol/L) their volume in creased by 17%, p < 0.05. Conclusion: Mesothelial cells shrink after exposure to hypertonic medium. I ncreased intracellular uptake of amino acids may be one of the regulatory m echanisms that ensure subsequent volume increase in these cells. Mesothelia l cells chronically exposed to hypertonic medium swell after transfer to a medium with physiologic osmolality.