Vasorelaxation of rat thoracic aorta caused by 14-deoxyandrographolide.
1. The pharmacological effects of 14-deoxyandrographolide on rat isolated thoracic aorta were examined. 2. 14-Deoxyandrographolide (2.5-120 mumol/L) inhibited contractions induced by phenylephrine (PE; 0.1 mumol/L) and high K+ (80 mmol/L) in a concentration-dependent manner in endothelium-intact aorta. The effect was attenuated in endothelium-denuded aorta without modifying the maximal response. Like verapamil, 14-deoxyandrographolide produced a much greater vasorelaxant effect in aorta precontracted by KCl than by PE. 14-Deoxyandrographolide (20-60 mumol/L) also inhibited responses of the rat aorta to PE. 3. In Ca(2+)-free medium (KCl 55 mmol/L), 14-deoxyandrographolide (20-80 mumol/L) antagonized Ca(2+)-induced vasocontraction in a concentration-dependent manner and transient contractions induced by both caffeine (10 mmol/L) and nor-adrenaline (1 mumol/L) were suppressed or almost abolished by 14-deoxyandrographolide. 4. The vasorelaxant effect of 14-deoxyandrographolide was partially antagonized by NG-nitro-L-arginine methyl ester (25 mumol/L), a specific and competitive nitric oxide synthase (NOS) inhibitor, and methylene blue (10 mumol/L), a soluble guanylate cyclase inhibitor, but was not affected by indomethacin (20 mumol/L), a cyclo-oxygenase inhibitor, or glibenclamide (10 mumol/L), an ATP-sensitive K(+)-channel blocker. 5. These results suggest that the vasorelaxant activity of 14-deoxyandrographolide may be mediated via the activation of NOS and guanylate cyclase, as well as the blockade of Ca2+ influx through both voltage- and receptor-operated Ca2+ channels.
Department of Pharmacology, Faculty of Medicine, National University of Singapore, Singapore. phctankh@nus.edu.sg
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D000818:Animals; D001013:Aorta, Thoracic / Q000187:drug effects*; D002110:Caffeine / Q000494:pharmacology; D002118:Calcium / Q000502:physiology; D000697:Central Nervous System Stimulants / Q000494:pharmacology; D016861:Cyclooxygenase Inhibitors / Q000494:pharmacology; D004224:Diterpenes / Q000494:pharmacology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006162:Guanylate Cyclase / Q000037:antagonists & inhibitors; D066298:In Vitro Techniques; D008297:Male; D009126:Muscle Relaxation / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000187:drug effects*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors; D009638:Norepinephrine / Q000494:pharmacology; D010656:Phenylephrine / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D014662:Vasoconstrictor Agents / Q000494:pharmacology; D014665:Vasodilator Agents / Q000494:pharmacology*
C114791:14-deoxyandrographolide; D000697:Central Nervous System Stimulants; D016861:Cyclooxygenase Inhibitors; D004224:Diterpenes; D004791:Enzyme Inhibitors; D014662:Vasoconstrictor Agents; D014665:Vasodilator Agents; D010656:Phenylephrine; D002110:Caffeine; D019001:Nitric Oxide Synthase; D006162:Guanylate Cyclase; D002118:Calcium; D009638:Norepinephrine