Comparison of the inhibitory effect of ATP-dependent K+ channel blockers glibenclamide and chlorpropamide, on diazoxide-induced relaxation of rat ileum

Objective: This study was conducted to compare the potential inhibitory effect of ATP-dependent K+ channel blockers, glibenclamide and chlorpropamide on diazoxide-induced relaxation of isolated rat ileum. Material and Methods: The study was performed on rat ileum connected to an isotonic transducer and the contractions were recorded on one-channel MD2 recorder. In this study the relaxant effect of diazoxide on KCl-induced precontracted rat ileum, and its inhibition by different concentrations of glibenclamide and chlorpropamide were studied. Results: Diazoxide (10-5-10-3M) produced dose-dependent relaxation. EC50 for diazoxide-induced relaxation was 8 x 10-5M. Neither glibenclamide nor chlorpropamide had any effect on the resting tension of the rat ileum preparation. Both glibenclamide and chlorpropamide reversed diazoxide-induced relaxation. The pA2 values for glibenclamide and chlorpropamide reversal of diazoxide induced- relaxation were 6.3 and 5 respectively. Conclusion: The results confirm that the inhibitory effect of glibenclamide on diazoxide-induced relaxation in rat ileum is higher than that of chlorpropamide.