Effect of glibenclamide on the osmotic resistance of pancreatic beta-cells.

The effect of glibenclamide on the osmotic resistance of beta-cells was measured using isolated beta-cells from ob/ob-mice. The beta-cells were incubated at different osmolarity and the diameters of the approximately spherical beta-cells were measured at 22 degrees C or at 37 degrees C with the aid of a screw micrometer eyepiece fitted to a light microscope. A near linear decrease of beta-cell diameter was found with increasing osmolarity (111-617 mosm/l). Control experiments showed that the membrane stabilizers, imipramine (0.1 mmol/l) or tetracaine (1 mmol/l), strongly reduced the osmotic swelling induced by low osmolarity (180 mosm/l). Glibenclamide (0.001 or 0.2 mmol/l) did not affect the beta-cell diameter at normal osmolarity (317 mosm/l) but reduced the swelling induced by hypoosmolarity (180 mosm/l) and the shrinking induced by hyperosmolarity (617 mosm/l). It is suggested that glibenclamide increases the osmotic resistance of isolated beta-cells by changing transmembrane flow of ions.