Objective:To study the effects of
nucleotides on the specific glibenclamide (Gli) binding to rat cardiac ventricular membranes
Methods:Radioligand binding techniques including competitive or/and kinetic assay of association and
dissociation were employed to determine the modulation of ATP, ADP, UDP, AMP and adenosine (Ade) on the specific Gli binding to rat cardiac ventricular membranes, respectively Results: It was observed that Gli bound reversibly and specifically to cardiac membranes and unlabeled Gli displaced the specific Gli binding completely with IC 50 of 195 nmol/L Under the same conditions, ATP, ADP and UDP (from 0 01 to 5 mmol/L) concentration dependently inhibited Gli binding and the values of IC 50 were 1 68, 0 80 and 2 08 mmol/L,respectively, whereas AMP and Ade did not inhibit the binding up to 1 mmol/L Analysis of the kinetic experiment showed that the time of Gli association and dissociation in cardiac preparations conformed to first order kinetics The association was delayed and the dissociation kept unchanged by ATP, ADP and UDP of 1 mmol/L,respectively Conclusion:It is suggested that ATP, ADP and UDP could change the conformation of SUR and thus regulate the specific binding of Gli in the negative allosteric manner in cardiac membranes