A specific binding site for K+ channel openers in rat aorta.

Department of Preclinical Research, Sandoz Pharma Ltd., Basel, Switzerland.
The K+ channel openers, including cromakalim, pinacidil, minoxidil sulfate, diazoxide, and nicorandil, form a chemically heterogeneous group of compounds, which relax smooth muscle by opening plasmalemmal K+ channels. At present it is not known whether these drugs elicit their effects by binding to the same target, presumably the K+ channel. In order to address this question, a binding assay for K+ channel openers has been developed in vascular smooth muscle. The novel tritiated K+ channel opener, [3H]P1075, an analogue of pinacidil, binds with high affinity (KD = 6 +/- 1 nM) to endothelium-denuded rings of rat aorta. Inhibition studies indicate that the different families of K+ channel openers bind to a common target. Evidence is presented to suggest that the binding site for the sulfonylurea, glibenclamide, the major blocker of the K+ channel openers, is coupled in a negative allosteric manner to the binding site(s) for the openers. The binding assay described here may open the way to the biochemical characterization of the drug receptor for the K+ channel openers.
Mesh Terms:
Animals, Aorta, Binding Sites, Glyburide, Guanidines, In Vitro Techniques, Kinetics, Male, Muscle, Smooth, Vascular, Potassium Channels, Pyridines, Rats, Rats, Inbred Strains
J. Biol. Chem. Jun. 15, 1992; 267(17);11689-92 [PUBMED:1601843]
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