In vitro study of the mechanism of potassium transport into human mesothelial cells. I: Effect of hyperosmolality

Objective: To study the mechanism(s) of potassium transport into human mesothelial cells (HMC) exposed to osmotic solutes. Design: Using potassium analog ⁸⁶Rb, we evaluated its intracellular transport through three pathways: 1. blocked by ouabain; 2. blocked by furosemide but not by ouabain, 3. blocked by neither furosemide nor ouabain. Experiments were performed in a normotonic medium (control) or in a medium supplemented with osmotic solutes (glucose, glycerol, mannitol). Both the acute and chronic effects of osmotic solutes on potassium transport were studied. Results: The acute exposure of mesothelial cells to osmotic solutes modifies the intracellular transport of potassium through all studied channels, and the effect is specific for every solute. In mesothelial cells exposed over 7 days to glucose (90 mM), the intracellular transport via ouabain- and furosemide-blocked channels is decreased, whereas it is increased through the third pathway. Total intracellular accumulation of ⁸⁶Rb (potassium) ions in mesothelial cells cultured in a medium supplemented with various concentrations of glucose is decreased, and this effect is proportional to the concentration of glucose in the medium. Conclusions: The intracellular transport of potassium in mesothelial cells is regulated through at least three independent mechanisms. Acute or chronic exposure of mesothelial cells to a hypertonic medium affects the intracellular accumulation of potassium, and this effect is specific for the various osmotic solutes.