Protonophoretic activity of hypoglycemic sulfonylureas in black lipid membranes.

The ability of glibenclamide and of gliclazide to act as protonophores has been studied in black lipid membranes made of glycerol monoleate as a function of pH and drug concentration. Protons may effectively be transported across lipid membranes with a maximum at a pH close to the pKa of the sulfamide (pKa of glibenclamide = 5.4). It is suggested therefore that hypoglycemic sulfonylureas may act in part as Ca2+ inward and H+ outward ionophores through plasma membranes of pancreatic B cells.