Extracellular K(+)-induced hyperpolarizations and dilatations of rat coronary and cerebral arteries involve inward rectifier K(+) channels.
1. The hypothesis that inward rectifier K(+) channels are involved in the vasodilatation of small coronary and cerebral arteries (100-200 microm diameter) in response to elevated [K+]o was tested. The diameters and membrane potentials of pressurized arteries from rat were measured using a video-imaging system and conventional microelectrodes, respectively. 2. Elevation of [K+]o from 6 to 16 mM caused the membrane potential of pressurized (60 mmHg) arteries to hyperpolarize by 12-14 mV. Extracellular Ba(2+) (Ba2+(o)) blocked K(+)-induced membrane potential hyperpolarizations at concentrations (IC(50), 6 microM) that block inward rectifier K(+) currents in smooth muscle cells isolated from these arteries. 3. Elevation of [K+]o from 6 to 16 mM caused sustained dilatations of pressurized coronary and cerebral arteries with diameters increasing from 125 to 192 microm and 110 to 180 microm in coronary and cerebral arteries, respectively. Ba2+(o) blocked K(+)-induced dilatations of pressurized coronary and cerebral arteries (IC50, 3-8 microM). 4. Elevated [K+]o-induced vasodilatation was not prevented by blockers of other types of K(+) channels (1 mM 4-aminopyridine, 1 mM TEA+, and 10 mu M glibenclamide), and blockers of Na(+)-K(+)-ATPase. Elevated [K+]o-induced vasodilatation was unaffected by removal of the endothelium. 5. These findings suggest that K+(o) dilates small rat coronary and cerebral arteries through activation of inward rectifier K(+) channels. Furthermore, these results support the hypothesis that inward rectifier K(+) channels may be involved in metabolic regulation of coronary and cerebral blood flow in response to changes in [K+]o.
Knot
H J
HJ
Department of Pharmacology, University of Vermont, Colchester, VT 05446-2500, USA. knot@northpole.med.uvm.edu
Zimmermann
P A
PA
Nelson
M T
MT
D000818:Animals; D001158:Arteries / Q000187:drug effects / Q000502:physiology; D001464:Barium / Q000494:pharmacology; D002536:Cerebral Arteries / Q000187:drug effects / Q000502:physiology*; D003331:Coronary Vessels / Q000187:drug effects / Q000502:physiology*; D004594:Electrophysiology; D004730:Endothelium, Vascular / Q000502:physiology; D005110:Extracellular Space / Q000378:metabolism*; D005260:Female; D011188:Potassium / Q000502:physiology*; D026902:Potassium Channel Blockers; D015221:Potassium Channels / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D000254:Sodium-Potassium-Exchanging ATPase / Q000037:antagonists & inhibitors; D014664:Vasodilation / Q000187:drug effects
D026902:Potassium Channel Blockers; D015221:Potassium Channels; D001464:Barium; D000254:Sodium-Potassium-Exchanging ATPase; D011188:Potassium