Characterization of bradykinin-induced endothelium-independent contraction in equine basilar artery.
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 F(2alpha). The maximal response and pD(2) value were 161.2 +/- 28.1% (to 60 mm KCl-induced contraction) and 8.24 +/- 0.25 respectively. The cumulative concentration-response curve for BK was not shifted to the right by des-Arg(9)-[Leu(8)]-BK (a B(1)-receptor antagonist), HOE140 (a B(2)-receptor antagonist) or NPC567 (another B(2)-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 A(2) inhibitor), tetrodotoxin (a selective blocker of Na(+) channels), guanethidine (a nor-adrenergic neuron blocking drug), phentolamine (an alpha-adrenoceptor antagonist), Nomega-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 B(1) and B(2) receptors. Arachidonic acid metabolites and neurotransmitters like norepinephrine and NO might not play a role in BK-induced contraction in equine basilar artery.
Ueno
D
D
Department of Veterinary Pharmacology, Faculty of Agriculture, Kagoshima University, Korimoto, Kagoshima, Japan.
Yabuki
A
A
Obi
T
T
Shiraishi
M
M
Nishio
A
A
Miyamoto
A
A
D000003:Abattoirs; D000704:Analysis of Variance; D000818:Animals; D001488:Basilar Artery / Q000187:drug effects* / Q000502:physiology; D001920:Bradykinin / Q000494:pharmacology*; D015237:Dinoprost / Q000008:administration & dosage; D004730:Endothelium, Vascular / Q000187:drug effects* / Q000502:physiology; D005260:Female; D006736:Horses / Q000502:physiology*; D008297:Male; D013552:Swine; D014665:Vasodilator Agents / Q000494:pharmacology*
D014665:Vasodilator Agents; D015237:Dinoprost; D001920:Bradykinin