EFFECTS OF OSMOTIC CHANGES IN EXTRACELLULAR SOLUTION ON ELECTRICAL-ACTIVITY OF MOUSE PANCREATIC B-CELLS

The influence of changes in the osmolarity of the extracellular soluti on on electrical activity of mouse pancreatic B-cells was studied with intracellular microelectrodes. In the presence of 15 mmol/l glucose t he membrane potential of B-cells oscillates. A reduction of the osmola rity by 40 mosmol/l caused a small temporary hyperpolarization in six out of eight cells. After 2 to 3 min electrical activity was increased in all cells. However, this effect was also transient. 5 to 8 min aft er onset of exposure to hypotonic solution the cells repolarized again and electrical activity decreased. Increasing the osmolarity of the e xtracellular solution by 40 mosmol/l led to a sustained and reversible depolarization of the membrane potential. However, the electrical act ivity was transiently suppressed. The changes in electrical activity o bserved in hypotonic solution might explain the previously described t ransient rise in insulin secretion provoked by osmotic cell swelling. (C) 1994 Academic Press, Inc.