Potassium and chloride fluxes are involved in volume regulation in mouse pancreatic islet cells

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Abstract
Potassium and chloride transport were measured in β‐cell‐rich islets from ob/ob‐mice using 36Cl‐86Rb+ (K+‐analogue). Reduction of the osmolarity from the normal 317 mosm l‐1 to 180 mosm l‐1 reduced the apparent content of K+ Cl1. Hypo‐osmolarity had no effect on the ouabain‐sensitive portion of the Rb+ influx (Na+/K+ pump), but reduced the ouabain‐resistant portion of the influx. Hypo‐osmolarity also strongly increased the Rb+ efflux rate. Both tetracaine (0.5 mitt) and glibenclamide (20 μM), which increase the osmotic resistance of pancreatic β cells, significantly potentiated the reduction in apparent K+ content induced by hypo‐osmolarity. This study suggests that the volume regulation in pancreatic β cells is partly due to K+ Cl‐ flux and that glibenclamide and tetracaine increase the osmotic resistance of the β cells by affecting such ion transport.