title: The role of L- and T-type calcium channels in local and remote calcium responses in rat mesenteric terminal arterioles.
abstract: OBJECTIVE
  The roles of intercellular communication and T-type versus L-type voltage-dependent Ca(2+) channels (VDCCs) in conducted vasoconstriction to local KCl-induced depolarization were investigated in mesenteric arterioles.
  
  
  METHODS
  Ratiometric Ca(2+) imaging (R) using Fura-PE3 with micro-ejection of depolarizing KCl solution and VDCC blockers, and immunohistochemical and RT-PCR techniques were applied to isolated rat mesenteric terminal arterioles (n = 71 from 47 rats; intraluminal diameter: 24 +/- 1 microm; length: 550-700 microm).
  
  
  RESULTS
  Local application of KCl (at 0 microm) led to local (DeltaR = 0.54) and remote (DeltaR = 0.17 at 500 microm) increases in intracellular Ca(2+). Remote Ca(2+) responses were inhibited by the gap junction uncouplers carbenoxolone and palmitoleic acid. Ca(V)1.2, Ca(V)3.1 and Ca(V)3.2 channels were immunolocalized in vascular smooth muscle cells and Ca(V)3.2 in adjacent endothelial cells. Local and remote Ca(2+) responses were inhibited by bath application of L- and T-type blockers [nifedipine, NNC 55-0396 and R(-)-efonidipine]. Remote Ca(2+) responses (500 microm) were not affected by abolishing Ca(2+) entry at an intermediate position on the arterioles (at 200-300 microm) using micro-application of VDCC blockers.
  
  
  CONCLUSIONS
  Both L- and T-type channels mediate Ca(2+) entry during conducted vasoconstriction to local KCl in mesenteric arterioles. However, these channels do not participate in the conduction process per se.
authors.affiliation: Division of Renal and Vascular Research, Department of Biomedical Sciences, Panum Institute, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Thomas Hartig
authors.initials: TH
authors.lastname: Braunstein
authors.forename: Ryuji
authors.initials: R
authors.lastname: Inoue
authors.forename: Leanne
authors.initials: L
authors.lastname: Cribbs
authors.forename: Masahiro
authors.initials: M
authors.lastname: Oike
authors.forename: Yushi
authors.initials: Y
authors.lastname: Ito
authors.forename: Niels-Henrik
authors.initials: NH
authors.lastname: Holstein-Rathlou
authors.forename: Lars Jørn
authors.initials: LJ
authors.lastname: Jensen