A specific binding site for K+ channel openers in rat aorta.
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.
Bray
K M
KM
Department of Preclinical Research, Sandoz Pharma Ltd., Basel, Switzerland.
Quast
U
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D000818:Animals; D001011:Aorta; D001665:Binding Sites; D005905:Glyburide / Q000494:pharmacology; D006146:Guanidines / Q000494:pharmacology; D066298:In Vitro Techniques; D007700:Kinetics; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000378:metabolism*; D015221:Potassium Channels / Q000187:drug effects*; D011725:Pyridines / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains
D006146:Guanidines; D015221:Potassium Channels; D011725:Pyridines; C073896:N-cyano-N'-(1,1-dimethylpropyl)-N''-(3-pyridinyl)guanidine; D005905:Glyburide