TY - JOUR
T1 - BKCa and KV channels limit conducted vasomotor responses in rat mesenteric terminal arterioles
AU - Hald, Bjørn Olav
AU - Jacobsen, Jens Christian Brings
AU - Braunstein, Thomas Hartig
AU - Inoue, Ryuji
AU - Ito, Yuski
AU - Sørensen, Preben Graae
AU - von Holstein-Rathlou, Niels-Henrik
AU - Jensen, Lars Jørn
PY - 2012
Y1 - 2012
N2 - Intracellular Ca(2+) signals underlying conducted vasoconstriction to local application of a brief depolarizing KCl stimulus was investigated in rat mesenteric terminal arterioles (<40 µm). Using a computer model of an arteriole segment comprised of coupled endothelial cells (EC) and vascular smooth muscle cells (VSMC) simulations of both membrane potential and intracellular [Ca(2+)] were performed. The "characteristic" length constant, ¿, was approximated using a modified cable equation in both experiments and simulations. We hypothesized that K(+) conductance in the arteriolar wall limit the electrotonic spread of a local depolarization along arterioles by current dissipation across the VSMC plasma membrane. Thus, we anticipated an increased ¿ by inhibition of voltage-activated K(+) channels. Application of the BK(Ca) channel blocker iberiotoxin (100 nM) onto mesenteric arterioles in vitro and inhibition of BK(Ca) channel current in silico increased ¿ by 34% and 32%, respectively. Similarly, inhibition of K(V) channels in vitro (4-aminopyridine, 1 mM) or in silico increased ¿ by 41% and 21%, respectively. Immunofluorescence microscopy demonstrated expression of BK(Ca), Kv1.5, Kv2.1, but not Kv1.2, in VSMCs of rat mesenteric terminal arterioles. Our results demonstrate that inhibition of voltage-activated K(+) channels enhance vascular-conducted responses to local depolarization in terminal arterioles by increasing the membrane resistance of VSMCs. These data contribute to our understanding of how differential expression patterns of voltage-activated K(+) channels may influence conducted vasoconstriction in small arteriolar networks. This finding is potentially relevant to understanding the compromised microcirculatory blood flow in systemic vascular diseases such as diabetes mellitus and hypertension.
AB - Intracellular Ca(2+) signals underlying conducted vasoconstriction to local application of a brief depolarizing KCl stimulus was investigated in rat mesenteric terminal arterioles (<40 µm). Using a computer model of an arteriole segment comprised of coupled endothelial cells (EC) and vascular smooth muscle cells (VSMC) simulations of both membrane potential and intracellular [Ca(2+)] were performed. The "characteristic" length constant, ¿, was approximated using a modified cable equation in both experiments and simulations. We hypothesized that K(+) conductance in the arteriolar wall limit the electrotonic spread of a local depolarization along arterioles by current dissipation across the VSMC plasma membrane. Thus, we anticipated an increased ¿ by inhibition of voltage-activated K(+) channels. Application of the BK(Ca) channel blocker iberiotoxin (100 nM) onto mesenteric arterioles in vitro and inhibition of BK(Ca) channel current in silico increased ¿ by 34% and 32%, respectively. Similarly, inhibition of K(V) channels in vitro (4-aminopyridine, 1 mM) or in silico increased ¿ by 41% and 21%, respectively. Immunofluorescence microscopy demonstrated expression of BK(Ca), Kv1.5, Kv2.1, but not Kv1.2, in VSMCs of rat mesenteric terminal arterioles. Our results demonstrate that inhibition of voltage-activated K(+) channels enhance vascular-conducted responses to local depolarization in terminal arterioles by increasing the membrane resistance of VSMCs. These data contribute to our understanding of how differential expression patterns of voltage-activated K(+) channels may influence conducted vasoconstriction in small arteriolar networks. This finding is potentially relevant to understanding the compromised microcirculatory blood flow in systemic vascular diseases such as diabetes mellitus and hypertension.
KW - Former LIFE faculty
KW - Calcium
KW - Terminal arterioe
KW - Conducted vasoconstriction
KW - Intercellula communication
KW - Electronic conduction
KW - Computer model
KW - Simulation
U2 - 10.1007/s00424-011-1049-8
DO - 10.1007/s00424-011-1049-8
M3 - Journal article
VL - 463
SP - 279
EP - 295
JO - Pflügers Archiv - European Journal of Physiology
JF - Pflügers Archiv - European Journal of Physiology
SN - 0031-6768
IS - 2
ER -