Identification of high and low (GTP-sensitive) affinity [3H]glibenclamide binding sites in cardiac ventricular membranes

Glibenclamide is an antagonist of the ATP-modulated K+ channel in cardiac tissue. This study showed glibenclamide to bind to high (0.2 nM) and low (40 nM) affinity binding sites in canine ventricular membranes. Gpp NH]p significantly altered the binding characteristics of the low affinity site, while those of the high affinity site were unchanged. This indicates independence of the two sites and suggests the low affinity site may be coupled to a G-binding protein. Although we have identified two 3H]glibenclamide binding sites, the importance of these sites to the cardiac effects of glibenclamide remains to be determined.