Enhanced spontaneous Ca2+ events in endothelial cells reflect signalling through myoendothelial gap junctions in pressurized mesenteric arteries

Cell Calcium. 2008 Aug;44(2):135-46. doi: 10.1016/j.ceca.2007.11.012. Epub 2008 Jan 11.


Increases in global Ca(2+) in the endothelium are a crucial step in releasing relaxing factors to modulate arterial tone. In the present study we investigated spontaneous Ca(2+) events in endothelial cells, and the contribution of smooth muscle cells to these Ca(2+) events, in pressurized rat mesenteric resistance arteries. Spontaneous Ca(2+) events were observed under resting conditions in 34% of cells. These Ca(2+) events were absent in arteries preincubated with either cyclopiazonic acid or U-73122, but were unaffected by ryanodine or nicotinamide. Stimulation of smooth muscle cell depolarization and contraction with either phenylephrine or high concentrations of KCl significantly increased the frequency of endothelial cell Ca(2+) events. The putative gap junction uncouplers carbenoxolone and 18alpha-glycyrrhetinic acid each inhibited spontaneous and evoked Ca(2+) events, and the movement of calcein from endothelial to smooth muscle cells. In addition, spontaneous Ca(2+) events were diminished by nifedipine, lowering extracellular Ca(2+) levels, or by blockers of non-selective Ca(2+) influx pathways. These findings suggest that in pressurized rat mesenteric arteries, spontaneous Ca(2+) events in the endothelial cells appear to originate from endoplasmic reticulum IP(3) receptors, and are subject to regulation by surrounding smooth muscle cells via myoendothelial gap junctions, even under basal conditions.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Anti-Ulcer Agents / pharmacology
  • Calcium / metabolism*
  • Carbenoxolone / pharmacology
  • Endoplasmic Reticulum / metabolism
  • Endothelium, Vascular / cytology
  • Endothelium, Vascular / drug effects
  • Endothelium, Vascular / metabolism*
  • Gap Junctions / physiology*
  • Glycyrrhetinic Acid / analogs & derivatives
  • Glycyrrhetinic Acid / pharmacology
  • Inositol 1,4,5-Trisphosphate Receptors / metabolism
  • Male
  • Mesenteric Arteries / cytology
  • Mesenteric Arteries / drug effects
  • Mesenteric Arteries / metabolism*
  • Muscle, Smooth, Vascular / cytology
  • Muscle, Smooth, Vascular / drug effects
  • Muscle, Smooth, Vascular / metabolism*
  • Rats
  • Rats, Wistar
  • Signal Transduction


  • Anti-Ulcer Agents
  • Inositol 1,4,5-Trisphosphate Receptors
  • 18alpha-glycyrrhetinic acid
  • Carbenoxolone
  • Glycyrrhetinic Acid
  • Calcium