Functional activity of Ca2+-dependent K+ channels is increased in basilar artery during chronic hypertension.
We examined the hypothesis that activity of Ca2+-dependent K+ channels is increased in the basilar artery during chronic hypertension. Diameter of the basilar artery was measured using a cranial window in anesthetized normotensive Wistar-Kyoto rats (WKY, arterial pressure = 109 +/- 3 mmHg, mean +/- SE) and stroke-prone spontaneously hypertensive rats (SHRSP, arterial pressure = 179 +/- 4 mmHg). Responses of the basilar artery to topical application of tetraethylammonium ion (TEA), an inhibitor of Ca2+-dependent K+ channels, were examined in WKY and SHRSP. Vessel diameter decreased by 2 +/- 1 and 4 +/- 0.1% in WKY and by 7 +/- 2 and 18 +/- 1% in SHRSP (P < 0.05 vs. WKY) in response to 10(-4) and 10(-3) M TEA, respectively. Similar results were obtained using iberiotoxin (10(-8) and 10(-7) M), a highly selective inhibitor of Ca2+-dependent K+ channels. In contrast to constrictor responses to TEA and iberiotoxin, constrictor responses of the basilar artery in response to serotonin and U-46619 were similar in WKY and SHRSP. In WKY rats that were made chronically hypertensive (arterial pressure = 172 +/- 6 mmHg) after treatment for 4 wk with N(G)-nitro-L-arginine methyl ester, an inhibitor of nitric oxide synthase, constriction of the basilar artery in response to TEA was also enhanced. These findings suggest that activity of Ca2+-dependent K+ channels is enhanced in the basilar artery in vivo in two models of chronic hypertension. Thus Ca2+-dependent K+ channels in the basilar artery may be activated during chronic hypertension, perhaps as a response to elevation of intracellular concentration of Ca2+.
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Department of Internal Medicine, University of Iowa College of Medicine, Iowa City 52242, USA.
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D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; D000818:Animals; D001488:Basilar Artery / Q000502:physiology / Q000503:physiopathology*; D002118:Calcium / Q000494:pharmacology*; D006973:Hypertension / Q000503:physiopathology*; D009119:Muscle Contraction / Q000187:drug effects; D010455:Peptides / Q000494:pharmacology; D026902:Potassium Channel Blockers; D015221:Potassium Channels / Q000502:physiology*; D011450:Prostaglandin Endoperoxides, Synthetic / Q000494:pharmacology; D051381:Rats; D011918:Rats, Inbred SHR; D011921:Rats, Inbred WKY; D012701:Serotonin / Q000494:pharmacology; D019789:Tetraethylammonium; D013757:Tetraethylammonium Compounds / Q000494:pharmacology; D013928:Thromboxane A2 / Q000031:analogs & derivatives / Q000494:pharmacology; D014661:Vasoconstriction / Q000187:drug effects*; D014662:Vasoconstrictor Agents / Q000494:pharmacology; D014862:Wasp Venoms / Q000494:pharmacology
D010455:Peptides; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D011450:Prostaglandin Endoperoxides, Synthetic; D013757:Tetraethylammonium Compounds; D014662:Vasoconstrictor Agents; D014862:Wasp Venoms; D012701:Serotonin; D013928:Thromboxane A2; D019789:Tetraethylammonium; D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; C064719:iberiotoxin; D002118:Calcium