Volume regulation in mouse pancreatic islet cells as studied by a new technique of microperifusion.

A new technique was designed to analyse whether pancreatic islet cells are able to regulate their volume in anisotonic media. The projected cell area of individual cells was continuously observed, and the corresponding volume calculated during microperifusion with media of different osmolarities. In isotonic medium (317 mosmol) the cell volume was stable during perifusion and decreased by 17 or 25% when the osmolarity was increased (sucrose) to 417 or 517 mosmol. Reducing the medium osmolarity to 285 mosmol resulted in a volume reduction of about 7%. No evidence for cell volume regulation was observed in these media. However, reducing the medium osmolarity to 262 mosmol induced an immediate and rapid cell swelling of approximately 14%, after which the initial cell volume was regained within 9 min. The data suggest that the pancreatic islet cells are equipped with mechanisms for regulatory volume decrease that appear to be activated when the cell volume is increased above a certain limit.