The role of L- and T-type calcium channels in local and remote calcium responses in rat mesenteric terminal arterioles.
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.
Braunstein
Thomas Hartig
TH
Division of Renal and Vascular Research, Department of Biomedical Sciences, Panum Institute, University of Copenhagen, Copenhagen, Denmark.
Inoue
Ryuji
R
Cribbs
Leanne
L
Oike
Masahiro
M
Ito
Yushi
Y
Holstein-Rathlou
Niels-Henrik
NH
Jensen
Lars Jørn
LJ