Tetraethylammonium-induced contraction of rabbit coronary artery.
The vasoactive effect of tetraethylammonium (TEA), a well-known K channel blocker, was tested on helical strips excised from the large epicardial coronary arteries of rabbit hearts. TEA (10 mM) induced transient tetanic contraction of greater amplitude as a result of summation of twitch responses. Occasionally, spontaneous periodic contractions occurred during prolonged exposure to 10 mM TEA. This TEA-induced contraction was abolished in Ca-free solution and suppressed by Ca-entry blockers: nitroglycerin, nicorandil, and isoproterenol, but not by phentolamine or atropine. In strips in which TEA did not induce remarkable contraction, subsequent addition of a subthreshold concentration of ergonovine, serotonin, acetylcholine, ouabain, K-rich solution, or alkalinization of the solution provoked remarkable contraction. These results are consistent with previous reports that TEA induced tetanic contraction as a result of summation of twitch responses due to spontaneous discharge of Ca-spikes in some arterial and tracheal smooth muscle. The results also support the idea that TEA-induced contraction of the rabbit coronary artery is mediated by the same mechanism, i.e., spontaneous Ca-spike discharge.
Iwaki
M
M
2nd Department of Internal Medicine, School of Medicine, University of Tokushima, Japan.
Nakaya
Y
Y
Kawano
K
K
Mizobuchi
S
S
Nakaya
S
S
Mori
H
H
D000818:Animals; D001158:Arteries / Q000187:drug effects; D003331:Coronary Vessels / Q000187:drug effects*; D004874:Ergonovine / Q000494:pharmacology; D007545:Isoproterenol / Q000494:pharmacology; D009119:Muscle Contraction / Q000187:drug effects*; D009131:Muscle, Smooth, Vascular / Q000187:drug effects*; D009536:Niacinamide / Q000031:analogs & derivatives / Q000494:pharmacology; D020108:Nicorandil; D005996:Nitroglycerin / Q000494:pharmacology; D011817:Rabbits; D013757:Tetraethylammonium Compounds / Q000494:pharmacology*; D014661:Vasoconstriction
D013757:Tetraethylammonium Compounds; D009536:Niacinamide; D020108:Nicorandil; D005996:Nitroglycerin; D007545:Isoproterenol; D004874:Ergonovine