Smooth Muscle Ca(2+)-Activated and Voltage-Gated K(+) Channels Modulate Conducted Dilation in Rat Isolated Small Mesenteric Arteries

T Z Beleznai, Polina L Yarova, Kathryn H Yuill, K A Dora

Research output: Contribution to journalArticlepeer-review

18 Citations (Scopus)

Abstract

Objective: To assess the influence of blocking smooth muscle large conductance Ca(2+)-activated K(+) channels and voltage-gated K(+) channels on the conducted dilation to ACh and isoproterenol. Materials and Methods: Rat mesenteric arteries were isolated with a bifurcation, triple-cannulated, pressurized and imaged using confocal microscopy. Phenylephrine was added to the superfusate to generate tone, and agonists perfused into a sidebranch to evoke local dilation and subsequent conducted dilation into the feed artery. Results: Both ACh- and isoproterenol-stimulated local and conducted dilation with similar magnitudes of decay with distance along the feed artery (2000 mu m: similar to 15% maximum dilation). The gap junction uncoupler carbenoxolone prevented both conducted dilation and intercellular spread of dye through gap junctions. IbTx, TEA or 4-AP, blockers of large conductance Ca(2+)-activated K(+) channels and voltage-gated K(+) channels, did not affect conducted dilation to either agonist. A combination of either IbTx or TEA with 4-AP markedly improved the extent of conducted dilation to both agonists (2000 mu m: > 50% maximum dilation). The enhanced conducted dilation was reflected in the hyperpolarization to ACh (2000 mu m: Control, 4 +/- 1 mV, n = 3; TEA with 4-AP, 14 +/- 3mV, n = 4), and was dependent on the endothelium. Conclusions: These data show that activated BKCa and KV-channels serve to reduce the effectiveness of conducted dilation.
Original languageEnglish
Pages (from-to)487-500
Number of pages14
JournalMicrocirculation
Volume18
Issue number6
DOIs
Publication statusPublished - Aug 2011

Keywords

  • K(+) channels
  • hyperpolarization
  • conducted response

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