title: Relaxation of rat thoracic aorta induced by pyridine.
abstract: The pharmacological and toxicological activity of pyridine was determined in rat thoracic aorta. Pyridine inhibited norepinephrine (3 microM)-induced phasic and tonic contractions in the thoracic aorta as well as the endothelium-denuded aorta of the rat. The tonic pre-contraction elicited by norepinephrine was also relaxed by the addition of pyridine and this relaxing effect was not affected by indomethacin (20 microM), NG-monomethyl-L-arginine acetate (50 microM) or methylene blue (50 microM). In high-K+ medium (80 mM), pyridine inhibited the Ca2+ concentration-dependent vasocontraction. Moreover, in Ca(2+)-free medium, the norepinephrine (3 microM)-induced phasic contraction was also suppressed by pyridine, while the caffeine (10 mM)-induced contraction remained unaffected. The cAMP and cGMP levels of rat aorta were not changed by pyridine. The 45Ca2+ influx elicited by either norepinephrine or high-K+ was inhibited by pyridine in a concentration-dependent manner. All of these findings indicated that pyridine relaxes rat thoracic aorta by virtue of its Ca2+ channel-blocking properties in vascular smooth muscle.
authors.affiliation: Institute of Pharmacology, College of Medicine, National Taiwan University, Taipei.
authors.forename: K S
authors.initials: KS
authors.lastname: Hsu
authors.forename: S Y
authors.initials: SY
authors.lastname: Lin-Shiau
mesh_terms: D000818:Animals; D001013:Aorta, Thoracic / Q000187:drug effects / Q000378:metabolism; D002110:Caffeine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D000242:Cyclic AMP / Q000378:metabolism; D006152:Cyclic GMP / Q000378:metabolism; D004730:Endothelium, Vascular / Q000502:physiology; D005260:Female; D066298:In Vitro Techniques; D008297:Male; D009126:Muscle Relaxation / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000187:drug effects* / Q000378:metabolism; D009638:Norepinephrine / Q000037:antagonists & inhibitors / Q000494:pharmacology; D011188:Potassium / Q000037:antagonists & inhibitors / Q000494:pharmacology; D011725:Pyridines / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar
chemical_list: D011725:Pyridines; D002110:Caffeine; D000242:Cyclic AMP; D006152:Cyclic GMP; C023666:pyridine; D011188:Potassium; D002118:Calcium; D009638:Norepinephrine