G. Edwards et al., Role of gap junctions and EETs in endothelium-dependent hyperpolarization of porcine coronary artery, BR J PHARM, 129(6), 2000, pp. 1145-1154
1 The effects of endothelium-derived hyperpolarizing factor (EDHF: elicited
using substance P or bradykinin) were compared with those of 11,12-EET in
pig coronary artery. Smooth muscle cells were usually impaled with microele
ctrodes through the adventitial surface.
2 Substance P (100 nM) and 11,12-EET (11,12-epoxyeicosatrienoic acid: 3 mu
M) hyperpolarized endothelial cells in intact arteries. These actions were
unaffected by 100 nM iberiotoxin but were abolished by charybdotoxin plus a
pamin (each 100 nM).
3 Substance P (100 nM) and bradykinin (30 nM) hyperpolarized intact artery
smooth muscle; Substance P had no effect after endothelium removal.
4 11,12-EET hyperpolarized de-endothelialized vessels by 12.6 +/- 0.3 mV, a
n effect abolished by 100 nM iberiotoxin. 11,12-EET hyperpolarized intact a
rteries by 18.6 +/- 0.8 mV, an action reduced by iberiotoxin, which was ine
ffective against substance P. Hyperpolarizations to 11,12-EET and substance
P were partially inhibited by 100 nM charybdotoxin and abolished by furthe
r addition of 100 nM apamin.
5 30 mu M barium plus 500 nM ouabain depolarized intact artery smooth muscl
e but responses to substance P and bradykinin were unchanged. 500 mu M gap
27 markedly reduced hyperpolarizations to substance P and bradykinin which
were abolished in the additional presence of barium plus ouabain.
6 Substance P-induced hyperpolarizations of smooth muscle cells immediately
below the internal elastic lamina were unaffected by gap 27, even in the p
resence of barium plus ouabain.
7 In pig coronary artery, 11,12-EET is not EDHF. Smooth muscle hyperpolariz
ations attributed to 'EDHF' are initiated by endothelial cell hyperpolariza
tion involving charybdotoxin- (but not iberiotoxin) and apamin-sensitive K channels. This may spread electrotonically pia myoendothelial gap junction
s but the involvement of an unknown endothelial factor cannot be excluded.