Antidiabetic sulfonylureas control action potential properties in heart cells via high affinity receptors that are linked to ATP-dependent K+ channels

Both avian and mammalian heart cells have high affinity receptors for antidiabetic sulfonylureas. The biochemical identification of these receptors has been carried out with [3H]glibenclamide. The Kd values for the most potent sulfonylureas, such as glibenclamide itself, are in the nanomolar range. Comparative studies of structure-function relationships indicate high similarities of binding properties between the sulfonylurea receptors in cardiac cells and insulinoma cells, respectively. The duration of the action potential of guinea pig cardiac cells was drastically reduced by decreasing intracellular ATP concentrations by perfusion or by blockade of oxidative phosphorylation. Glibenclamide was found to restore normal or nearly normal action potential properties in [ATP]in-depleted cardiac cells. Single channel recording using the patch-clamp technique has shown that this effect is associated with high affinity blockade of ATP-sensitive K+ channels by sulfonylureas.