[Non-saturable cooperative binding of tolbutamide to rat endocrine pancreas. Criteria of specificity].

The binding of 3H-tolbutamide to isolated islets, which shows a cooperative non-saturable pattern up to about 5 X 10(-5) M, was confirmed. Binding to exocrine pancreatic tissue shows much less cooperativity. Among congeners of tolbutamide, unlabelled carbutamide and chlorpropamide in isodynamic concentrations, as well as diazoxide in an exactly antagonistic amount, behave like tolbutamide 5 X 10(-5) M itselt by cancelling cooperativity when added to the labelled drug. Glipizide and glibenclamide do not.