Sj. Park et al., Hyperpolarization caused by serotonin contributes to endothelium-dependentrelaxations in the porcine coronary artery, ACT PHAR SI, 20(12), 1999, pp. 1093-1097
AIM: The present study was designed to investigate the contribution of memb
rane hyperpolarization Ito endothelium-dependent relaxations induced by ser
otonin in the porcine coronary artery, METHODS: Rings with and without endo
thelium of porcine coronary arteries were suspended in conventional organ c
hambers for the measurement of isometric force. The cell membrane potential
of the vascular smooth muscle cells was measured using glass microelectrod
es, in the presence of indometacin, ketanserin, and/or N-omega-nitro-L-argi
nine. RESULTS: Serotonin induced a transient endothelium-, and concentratio
n-dependent relaxation in rings contracted with prostaglandin F-2 alpha in
the presence of N-omega-nitro-L-arginine (maximal relaxation: 19 %). The N-
omega-nitro-L-arginine resistant relaxation was abolished by high K+ and te
trabutylammonium chloride. Serotonin also caused an endothelium-, concentra
tion-dependent membrane hyperpolarizations with a maximal amplitude of -8.8
mV. The nitro-L-arginine resistant relaxations and hyperpolarizations were
abolished by methiothepin, but not by glibenclamide. The time course of th
e endothelium-dependent relaxations and hyperpolarizations was similar. CON
CLUSION: These results suggest a contribution of cell membrane hyperpolariz
ation to the endothelium-dependent relaxations induced by serotonin in the
porcine coronary artery.