title: Contractile regulation of the Na(+)-K(+)-2Cl(-) cotransporter in vascular smooth muscle.
abstract: Vasoconstrictors activate the Na(+)-K(+)-2Cl(-) cotransporter NKCC1 in rat aortic smooth muscle, but the mechanism is unknown. Efflux of (86)Rb(+) from rat aorta in response to phenylephrine (PE) was measured in the absence and presence of bumetanide, a specific inhibitor of NKCC1. Removal of extracellular Ca(2+) completely abolished the activation of NKCC1 by PE. This was not due to inhibition of Ca(2+)-dependent K(+) channels since blocking these channels with Ba(2+) in Ca(2+)-replete solution did not prevent activation of NKCC1 by PE. Stimulation of NKCC1 by PE was inhibited 70% by 75 microM ML-9, 97% by 2 microM wortmannin, and 70% by 2 mM 2,3-butanedione monoxime, each of which inhibited isometric force generation in aortic rings. Bumetanide-insensitive Rb(+) efflux, an indication of Ca(2+)-dependent K(+) channel activity, was reduced by ML-9 but not by the other inhibitors. Stretching of aortic rings on tubing to increase lumen diameter to 120% of normal almost completely blocked the stimulation of NKCC1 by PE without inhibiting the stimulation by hypertonic shrinkage. We conclude that activation of the Na(+)-K(+)-2Cl(-) cotransporter by PE is the direct result of smooth muscle contraction through Ca(2+)-dependent activation of myosin light chain kinase. This indicates that the Na(+)-K(+)-2Cl(-) cotransporter is regulated by the contractile state of vascular smooth muscle.
authors.affiliation: Renal Division, Department of Medicine, Emory University School of Medicine, Atlanta, Georgia 30322, USA.
authors.forename: F
authors.initials: F
authors.lastname: Akar
authors.forename: G
authors.initials: G
authors.lastname: Jiang
authors.forename: R J
authors.initials: RJ
authors.lastname: Paul
authors.forename: W C
authors.initials: WC
authors.lastname: O'Neill
mesh_terms: D000730:Androstadienes / Q000494:pharmacology; D000818:Animals; D001011:Aorta / Q000187:drug effects / Q000378:metabolism / Q000502:physiology; D001381:Azepines / Q000494:pharmacology; D002034:Bumetanide / Q000494:pharmacology; D002352:Carrier Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D003931:Diacetyl / Q000031:analogs & derivatives / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D066298:In Vitro Techniques; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology; D009219:Myosin-Light-Chain Kinase / Q000037:antagonists & inhibitors / Q000502:physiology; D010656:Phenylephrine / Q000037:antagonists & inhibitors / Q000494:pharmacology; D010812:Physical Stimulation; D051381:Rats; D017207:Rats, Sprague-Dawley; D028021:Sodium-Potassium-Chloride Symporters; D014661:Vasoconstriction / Q000187:drug effects / Q000502:physiology*; D014662:Vasoconstrictor Agents / Q000494:pharmacology; D000077191:Wortmannin
chemical_list: D000730:Androstadienes; D001381:Azepines; D002352:Carrier Proteins; D004791:Enzyme Inhibitors; D028021:Sodium-Potassium-Chloride Symporters; D014662:Vasoconstrictor Agents; D002034:Bumetanide; C056218:ML 9; C004717:diacetylmonoxime; D010656:Phenylephrine; D009219:Myosin-Light-Chain Kinase; D003931:Diacetyl; D000077191:Wortmannin