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KMID : 0811719970010040393
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Korean Journal of Physiology & Pharmacology
1997 Volume.1 No. 4 p.393 ~ p.402
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Mechanisms Underlying Relaxations Caused by Angiotensin Ⅱ and Its Analogs in Isolated Rabbit Mesenteric Artery
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Ki Whan Hong
Ki Whan Hong/Ji Young Park/Chi Dae Kim/Won Suk Lee/Byung Yong Rhim/Sung-Eun Yoo
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Abstract
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In the present study, we characterized the angiotensin II (AII)-induced relaxations in the phenylephrine-precontracted rabbit mesenteric arteries with endothelium. 1) AII-induced relaxation was consistently observed in the rabbit mesenteric arteries with and without endothelium, but not in the aortic segment with endothelium. 2) AII-induced endothelium-dependent relaxation was markedly inhibited by Nw?nitro?L?arginine (L-NNA, 100μM), methylene blue (10μM) and LY83583 (10μM), respectively. 3) Inhibition of cyclooxygenase with indomethacin (10μM) strongly decreased the vasorelaxant response to AII irrespective of the presence of endothelium. 4) 7-Ethoxyresorufin (1μM) and clotrimazole (1μM), inhibitors of cytochrome P-450-dependent arachidonic acid metabolism, greatly attenuated the vasodilator response to AII. 5) Carbacyclin, arachidonic acid and prostaglandin F2α (PGF2α) caused concentration-dependent relaxations in the mesenteric artery with endothelium, which were inhibited by L-NNA and methylene blue. 6) AII and PGF2α significantly stimulated cyclic GMP formation in the mesenteric arteries with endothelium, which was inhibited by L-NNA and methylene blue, respectively. 7) AII enhanced synthesis of PGF2α and 6-keto PGF1α from the arterial segments with endothelium, which was inhibitable by indomethacin, but not by L-NNA. In conclusion, the vasorelaxant responses to AII of the rabbit mesenteric artery with endothelium are subserved by arachidonic acid and its metabolites produced via activation of cyclooxygenase and cytochrome P-450 enzyme as well as by nitric oxide.
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KEYWORD
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Angiotensin Ⅱ, Rabbit mesenteric artery, Vasorelaxation,
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