Abstract
Pressor effects of the vasoconstrictor hormone arginine vasopressin (AVP), observed when systemic AVP concentrations are less than 100 pM, are important for the physiological maintenance of blood pressure, and they are also the basis for therapeutic use of vasopressin to restore blood pressure in hypotensive patients. However, the mechanisms by which circulating AVP induces arterial constriction are unclear. We examined the novel hypothesis that KCNQ potassium channels mediate the physiological vasoconstrictor actions of AVP. Reverse transcriptase polymerase chain reaction revealed expression of KCNQ1, KCNQ4, and KCNQ5 in rat mesenteric artery smooth muscle cells (MASMCs). Whole-cell perforated patch recordings of voltage-sensitive K+ (Kv) currents in freshly isolated MASMCs revealed 1,3-dihydro-1-phenyl-3,3-bis(4-pyridinylmethyl)-2H-indol-2-one (linopirdine)- and 10,10-bis(4-pyridinylmethyl)-9(10H)-anthracenone (XE-991)-sensitive KCNQ currents that were electrophysiologically and pharmacologically distinct from other Kv currents. Suppression of KCNQ currents by AVP (100 pM) was associated with significant membrane depolarization, and it was abolished by the protein kinase C (PKC) inhibitor calphostin C (250 nM). The KCNQ channel blocker linopirdine (10 μM) inhibited KCNQ currents in MASMCs, and it induced constriction of isolated rat mesenteric arteries. The vasoconstrictor responses were not additive when combined with 30 pM AVP, and they were prevented by the L-type Ca2+ channel blocker verapamil. Ethyl-N-[2-amino-6-(4-fluorophenylmethylamino)pyridin-3-yl] carbamic acid (flupirtine) significantly enhanced KCNQ currents, and it reversed constrictor responses to 30 pM AVP. In vivo, i.v. administration of linopirdine induced a dose-dependent increase in mesenteric artery resistance and blood pressure, whereas flupirtine had the opposite effects. We conclude that physiological concentrations of AVP induce mesenteric artery constriction via PKC-dependent suppression of KCNQ currents and L-type Ca2+ channel activation in MASMCs.
Footnotes
-
This work was supported by the National Heart Lung and Blood Institute Grant R01 HL070670 (to K.L.B.) and the American Heart Association Grant 0715618Z (to A.R.M.).
-
The chemical structures for the KCNQ channel modulators (linopirdine, XE-991, and flupirtine) are provided in Munro and Dalby-Brown (2007).
-
Article, publication date, and citation information can be found at http://jpet.aspetjournals.org.
-
doi:10.1124/jpet.107.135764.
-
ABBREVIATIONS: Vm, membrane voltage; VSMC, vascular smooth muscle cell; Kv, voltage-sensitive K+; PIP2, phosphatidylinositol 4,5-bisphosphate; PLC, phospholipase C; AVP, arginine vasopressin; PKC, protein kinase C; MASMC, mesenteric artery smooth muscle cell; PCR, polymerase chain reaction; ANOVA, analysis of variance; 4-AP, 4-aminopyridine; PMA, phorbol 12-myristate 13-acetate; MA, mesenteric artery; DMSO, dimethyl sulfoxide; MVR, mesenteric vascular resistance; MAP, mean arterial pressure; HR, heart rate; KATP, ATP-sensitive K+; I-V, current-voltage; XE-991, 10,10-bis(4-pyridinylmethyl)-9(10H)-anthracenone; linopirdine, 1,3-dihydro-1-phenyl-3,3-bis(4-pyridinylmethyl)-2H-indol-2-one; flupirtine, ethyl-N-[2-amino-6-(4-fluorophenylmethylamino)pyridin-3-yl] carbamic acid.
-
↵ The online version of this article (available at http://jpet.aspetjournals.org) contains supplemental material.
-
↵1 Current affiliation: University of Illinois College of Medicine at Rockford, Rockford, Illinois.
- Received December 21, 2007.
- Accepted February 12, 2008.
- The American Society for Pharmacology and Experimental Therapeutics
JPET articles become freely available 12 months after publication, and remain freely available for 5 years.Non-open access articles that fall outside this five year window are available only to institutional subscribers and current ASPET members, or through the article purchase feature at the bottom of the page.
|