IN-VITRO STUDY OF THE MECHANISM OF POTASSIUM-TRANSPORT INTO HUMAN MESOTHELIAL CELLS .1. EFFECT OF HYPEROSMOLALITY

Objective: To study the mechanism(s) of potassium transport into human mesothelial cells (HMC) exposed to osmotic solutes. Design: Using pot assium analog Rb-86, we evaluated its intracellular transport through three pathways: 1. blocked by ouabain; 2. blocked by furosemide but no t by ouabain; 3. blocked by neither furosemide nor ouabain. Experiment s were performed in a normotonic medium (control) or in a medium suppl emented with osmotic solutes (glucose, glycerol, mannitol). Both the a cute and chronic effects of osmotic solutes on potassium transport wer e 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 mes othelial cells exposed over 7 days to glucose (90 mM), the intracellul ar transport via ouabain- and furosemide-blocked channels is decreased , whereas it is increased through the third pathway. Total intracellul ar accumulation of Rb-86 (potassium) ions in mesothelial cells culture d in a medium supplemented with various concentrations of glucose is d ecreased, and this effect is proportional to the concentration of gluc ose in the medium. Conclusions:The intracellular transport of potassiu m in mesothelial cells is regulated through at least three independent mechanisms. Acute or chronic exposure of mesothelial cells to a hyper tonic medium affects the intracellular accumulation of potassium, and this effect is specific for the various osmotic solutes.