title: Gap junctional communication controls the overall endothelial calcium response to vasoactive agonists.
abstract: OBJECTIVE
  A cytosolic calcium (Ca(2+)(i)) increase is an important activation signal for the endothelium. We investigated whether interendothelial spreading of the Ca(2+) signal via gap junctions (GJs) plays a role for the overall Ca(2+)(i) increase in response to vasoactive agonists.
  
  
  RESULTS
  In human umbilical vein endothelial cells (HUVECs), a Ca(2+)(i) increase (Fura2) in response to histamine or ATP occurred initially only in about 30% of the cells (initially responding cells) reflecting the cell fraction expressing H(1) or purinergic receptors (FACS/immunohistochemistry). In the remaining adjacent cells, Ca(2+)(i) increases occurred only after a delay of up to 5 s. Blockade of GJ communication (meclofenamic acid and heptanol, or H(2)O(2); verified by dye injection) did not affect responses in the initially responding cells but abolished the delayed Ca(2+)(i) response of the remaining adjacent cells. The resulting reduction in the global endothelial Ca(2+)(i) response significantly reduced the nitric oxide synthesis (assessed as cGMP levels). Similar Ca(2+)(i) results were obtained in the endothelium of freshly isolated mouse (C57BL/6) aortas stimulated with ATP. The receptor-independent Ca(2+)(i) response to ionomycin occurred simultaneously in all cells, regardless of GJ inhibition. In separate experiments, inhibition of the IP(3) receptor (xestospongin-C; 40, µmol/L) but not of the ryanodine receptor (ryanodine, 250 µmol/L) reduced the spread of the Ca(2+)(i) signal into adjacent cells over longer distances.
  
  
  CONCLUSIONS
  The global Ca(2+)(i) response of the endothelium to agonists is determined decisively by the functionality of GJs, thus establishing a new role for GJs in controlling endothelial activity and vasomotor function.
authors.affiliation: Walter-Brendel-Centre of Experimental Medicine, Ludwig-Maximilians-Universität, Marchioninistr. 27, 81377 Munich, Germany. kameritsch@lmu.de
authors.forename: Petra
authors.initials: P
authors.lastname: Kameritsch
authors.forename: Kristin
authors.initials: K
authors.lastname: Pogoda
authors.forename: Angela
authors.initials: A
authors.lastname: Ritter
authors.forename: Silvia
authors.initials: S
authors.lastname: Münzing
authors.forename: Ulrich
authors.initials: U
authors.lastname: Pohl
mesh_terms: D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D001011:Aorta / Q000166:cytology; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling / Q000187:drug effects* / Q000502:physiology; D002450:Cell Communication / Q000187:drug effects / Q000502:physiology; D042783:Endothelial Cells / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D005260:Female; D017629:Gap Junctions / Q000187:drug effects* / Q000378:metabolism; D006632:Histamine / Q000494:pharmacology; D017442:Histamine Agonists / Q000494:pharmacology; D061307:Human Umbilical Vein Endothelial Cells; D006801:Humans; D015544:Inositol 1,4,5-Trisphosphate / Q000378:metabolism; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D051379:Mice; D008810:Mice, Inbred C57BL; D009569:Nitric Oxide / Q000378:metabolism; D011969:Receptors, Histamine H1 / Q000502:physiology; D058473:Receptors, Purinergic P2Y2 / Q000502:physiology; D013314:Stress, Mechanical; D014662:Vasoconstrictor Agents / Q000494:pharmacology*
chemical_list: D017442:Histamine Agonists; D011969:Receptors, Histamine H1; D058473:Receptors, Purinergic P2Y2; D014662:Vasoconstrictor Agents; D009569:Nitric Oxide; D006632:Histamine; D015544:Inositol 1,4,5-Trisphosphate; D000255:Adenosine Triphosphate; D002118:Calcium