A mechanism for regulatory volume decrease in cultured lens epithelial cells

PURPOSE. To identify mechanisms contributing to regulatory volume decrease in lens epithelial cells. METHODS. Cells of the lens epithelial cell line aTN4 were cultured in four-well culture dishes in Dulbecco's Modified Eagle Medium containing 10% fetal bovine serum. After confluence cell water space was determined by measuring the equilibrium distribution of 3-O-methylglucose. Potassium influx and efflux in isotonic and hypotonic solutions were measured using 86 rubidium (86 Rb) as tracer. Total cell potassium and sodium content were determined with atomic absorption spectroscopy. Protein content per well was assayed with a modified Lowry assay and flux data and ion concentrations were normalized per mg of protein. RESULTS. Lens epithelial cells responded to hypotonic solutions with rapid swelling followed by regulatory volume decrease (RVD). During swelling and subsequent volume decrease the unidirectional Rb efflux was increased proportionaly to the osmotic challenge. Rubidium efflux was highly sensitive to changes in extracellular osmolarity and responded with a measurable activation to changes of 12.5 mOsm. No changes in 86 Rb influx were observed with small changes (