ATP-Gated Potassium Channels

ATP-gated channels are found in a variety of cell types including vascular smooth muscle (for reviews see Gopalakrishnan et al., 1993 Evans and Taylor, 

FIGURE 1 Representative ATP-gated potassium channel openers. 

---

Calcium channel antagonists relax smooth muscle by inhibiting calcium entry and, therefore, have similar functional effects and therapeutic applications to the ATP-gated potassium channel agonists just discussed. Calcium channel antagonists have been widely used therapeutically to treat cardiovascular disorders and were available prior to the discovery of compounds such as cromakalim. 

Sulfonylureas bind to a 140-kDa high-affinity sulfonylurea receptor (Figure 41-2) that is associated with a beta-cell inward rectifier ATP-sensitive potassium channel. Binding of a sulfonylurea inhibits the efflux of potassium ions through the channel and results in depolarization. Depolarization opens a voltage-gated calcium channel and results in calcium influx and the release of preformed insulin. 

---