TY - JOUR
T1 - Small-conductance Ca2+-dependent K+ channels activated by ATP in murine colonic smooth muscle
AU - Koh, S. D.
AU - Dick, G. M.
AU - Sanders, K. M.
PY - 1997
Y1 - 1997
N2 - The patch-clamp technique was used to determine the ionic conductances activated by ATP in murine colonic smooth muscle cells. Extracellular ATP, UTP, and 2-methylthioadenosine 5'-triphosphate (2-MeS-ATP) increased outward currents in cells with amphotericin B-perforated patches. ATP (0.5-1 mM) did not affect whole cell currents of cells dialyzed with solutions containing ethylene glycol-bis(β-aminoethyl ether)-N,N,N',N'-tetraacetic acid. Apamin (3 x 10-7 M) reduced the outward current activated by ATP by 32 ± 5%. Single channel recordings from cell-attached patches showed that ATP, UTP, and 2-MeS-ATP increased the open probability of small-conductance, Ca2+- dependent K+ channels with a slope conductance of 5.3 ± 0.02 pS. Caffeine (500 μM) enhanced the open probability of the small-conductance K+ channels, and ATP had no effect after caffeine. Pyridoxal phosphate 6- azophenyl-2',4'-disulfonic acid tetrasodium (PPADS, 10-4 M), a nonselective P2 receptor antagonist, prevented the increase in open probability caused by ATP and 2-MeS-ATP. PPADS had no effect on the response to caffeine. ATP- induced hyperpolarization in the murine colon may be mediated by P(2y)- induced release of Ca2+ from intracellular stores and activation of the 5.3-pS Ca2+-activated K+ channels.
AB - The patch-clamp technique was used to determine the ionic conductances activated by ATP in murine colonic smooth muscle cells. Extracellular ATP, UTP, and 2-methylthioadenosine 5'-triphosphate (2-MeS-ATP) increased outward currents in cells with amphotericin B-perforated patches. ATP (0.5-1 mM) did not affect whole cell currents of cells dialyzed with solutions containing ethylene glycol-bis(β-aminoethyl ether)-N,N,N',N'-tetraacetic acid. Apamin (3 x 10-7 M) reduced the outward current activated by ATP by 32 ± 5%. Single channel recordings from cell-attached patches showed that ATP, UTP, and 2-MeS-ATP increased the open probability of small-conductance, Ca2+- dependent K+ channels with a slope conductance of 5.3 ± 0.02 pS. Caffeine (500 μM) enhanced the open probability of the small-conductance K+ channels, and ATP had no effect after caffeine. Pyridoxal phosphate 6- azophenyl-2',4'-disulfonic acid tetrasodium (PPADS, 10-4 M), a nonselective P2 receptor antagonist, prevented the increase in open probability caused by ATP and 2-MeS-ATP. PPADS had no effect on the response to caffeine. ATP- induced hyperpolarization in the murine colon may be mediated by P(2y)- induced release of Ca2+ from intracellular stores and activation of the 5.3-pS Ca2+-activated K+ channels.
KW - Apamin
KW - Caffeine
KW - Enteric inhibitory neurotransmission
KW - Gastrointestinal motility
KW - Ion channels
KW - Purinergic receptors
UR - http://www.scopus.com/inward/record.url?scp=0031416622&partnerID=8YFLogxK
U2 - 10.1152/ajpcell.1997.273.6.c2010
DO - 10.1152/ajpcell.1997.273.6.c2010
M3 - Article
C2 - 9435508
AN - SCOPUS:0031416622
SN - 0363-6143
VL - 273
SP - C2010-C2021
JO - American Journal of Physiology - Cell Physiology
JF - American Journal of Physiology - Cell Physiology
IS - 6 42-6
ER -