An endothelium-dependent contraction induced by A-23187, a Ca++ ionophore in canine basilar artery.
In most isolated canine basilar arteries tested, Ca++ ionophore A-23187 induced a small relaxation followed by a transient contraction. Both contraction and relaxation were abolished by removal of endothelium. The endothelium-dependent contraction induced by A-23187 was attenuated by a phospholipase A2 inhibitor (quinacrine), cyclooxygenase inhibitors (aspirin and indomethacin), a thromboxane A2 (TXA2) synthetase inhibitor (OKY-046) and a TXA2 antagonist (ONO-3708). The A-23187-induced contraction was abolished by lowering the Ca++ concentration of medium to 10%, whereas the contraction induced by 9,11-epithio-11,12-methano-TXA2 (STA2) was attenuated slightly by lowering [Ca++]. The A-23187-induced contraction was reduced markedly by nifedipine (10(-9) to 10(-7) M), but the STA2-induced contraction was only attenuated slightly by nifedipine. Bay K 8644 did not affect the A-23187- and STA2-induced contractions. The present experiments demonstrate that A-23187 induced an endothelium-dependent contraction in canine basilar artery, and suggest that Ca++ might play a key role in production of an endothelium-derived contracting factor (probably TXA2).
Shirahase
H
H
Department of Pharmacology, Faculty of Medicine, Kyoto University, Japan.
Usui
H
H
Manabe
K
K
Kurahashi
K
K
Fujiwara
M
M
D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester / Q000494:pharmacology; D000818:Animals; D001241:Aspirin / Q000494:pharmacology; D001488:Basilar Artery / Q000187:drug effects*; D000001:Calcimycin / Q000494:pharmacology*; D004285:Dogs; D004730:Endothelium, Vascular / Q000187:drug effects* / Q000378:metabolism; D005260:Female; D008297:Male; D008689:Methacrylates / Q000494:pharmacology; D009543:Nifedipine / Q000494:pharmacology; D011796:Quinacrine / Q000494:pharmacology; D013928:Thromboxane A2 / Q000031:analogs & derivatives / Q000494:pharmacology; D014661:Vasoconstriction / Q000187:drug effects*
D008689:Methacrylates; D000001:Calcimycin; D013928:Thromboxane A2; D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester; C049855:ONO 3708; D011796:Quinacrine; D009543:Nifedipine; C034364:ozagrel; D001241:Aspirin