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Biochim Biophys Acta. 1998 Mar 6;1370(1):8-16.

Ion channels involved in insulin release are activated by osmotic swelling of pancreatic B-cells.

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Institute of Physiology, Gmelinstr. 5, University of Tübingen, D-72076 Tübingen, FRG.


Measurements of the membrane potential showed that osmotic swelling (-80 mosmol/l) of pancreatic B-cells led to a transient hyperpolarization followed by a more sustained depolarization of the cell membrane. Cell swelling triggers a transient activation of the K+ATP current and of an inward current, carried by Cl-. This current was inhibited by DIDS, D600, and by omission of extracellular Ca2+. The depolarization opens voltage dependent L-type Ca2+ channels, thereby increasing the intracellular Ca2+ activity ([Ca2+]i). This effect was blunted by D600 or abolished by omission of Ca2+. Moreover, osmotic swelling transiently increased the amplitude of the Ca2+ currents. Replacement of NaCl by d-mannitol proved that the observed effects are due to an increase in cell volume and not to a reduction of extracellular Na+ or Cl-. Our results suggest that regulatory volume decrease is achieved by activation of K+ and Cl- currents. The Cl- current is responsible for the previously described depolarization and increase in insulin release induced by osmotic cell swelling.

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