Characterization of bradykinin-induced endothelium-independent contraction in equine basilar artery

• Published in: Journal of veterinary pharmacology and therapeutics 2009-06, Vol.32 (3), p.264-270
• Main Authors: UENO, D, YABUKI, A, OBI, T, SHIRAISHI, M, NISHIO, A, MIYAMOTO, A
• Format: Article
• Language: English
• Subjects: Abattoirs; Analysis of Variance; Animals; arachidonic acid; arterial rings; arteries; basilar artery; Basilar Artery - drug effects; Basilar Artery - physiology; bradykinin; Bradykinin - pharmacology; Dinoprost - administration & dosage; endothelial cells; endothelial denudation; endothelium; Endothelium, Vascular - drug effects; Endothelium, Vascular - physiology; Female; guanethidine; horses; Horses - physiology; indomethacin; Male; metabolites; muscle contraction; neurotransmitters; nordihydroguaiaretic acid; norepinephrine; pharmacokinetics; phentolamine; prostaglandins; quinacrine; resting vascular tone; Swine; tetrodotoxin; Vasodilator Agents - pharmacology
• ISSN: 0140-7783; 1365-2885
• DOI: 10.1111/j.1365-2885.2008.01037.x

We investigated the effect of bradykinin (BK) on isolated equine basilar arterial rings with and without endothelium. BK induced concentration-dependent contraction of resting arterial rings and no relaxation when the rings were precontracted by prostaglandin F₂α. The maximal response and pD₂ value were 161.2 ± 28.1% (to 60 m m KCl-induced contraction) and 8.24 ± 0.25 respectively. The cumulative concentration-response curve for BK was not shifted to the right by des-Arg⁹-[Leu⁸]-BK (a B₁-receptor antagonist), HOE140 (a B₂-receptor antagonist) or NPC567 (another B₂-receptor antagonist). In four of six basilar arteries, NPC567 induced concentration-dependent contraction. Indomethacin (a cyclooxygenase inhibitor), nordihydroguaiaretic acid (a lipoxygenase inhibitor), quinacrine (a phospholipase A₂ inhibitor), tetrodotoxin (a selective blocker of Na⁺ channels), guanethidine (a nor-adrenergic neuron blocking drug), phentolamine (an α-adrenoceptor antagonist), Nω-nitro- l-arginine ( l-NNA, a nitric oxide (NO) synthase inhibitor) and endothelial denudation did not affect the BK-induced contraction. l-NNA and indomethacin induced contraction and relaxation under resting vascular tone respectively. These results suggest that endothelial cells are not involved in BK-induced contraction and that the contraction is not mediated via activation of known B₁ and B₂ receptors. Arachidonic acid metabolites and neurotransmitters like norepinephrine and NO might not play a role in BK-induced contraction in equine basilar artery.