title: Paraoxon attenuates vascular smooth muscle contraction through inhibiting Ca2+ influx in the rabbit thoracic aorta.
abstract: We investigated the effect of paraoxon on vascular contractility using organ baths in thoracic aortic rings of rabbits and examined the effect of paraoxon on calcium homeostasis using a whole-cell patch-clamp technique in isolated aortic smooth muscle cells of rabbits. The findings show that administration of paraoxon (30 microM) attenuated thoracic aorta contraction induced by phenylephrine (1 microM) and/or a high K+ environment (80 mM) in both the presence and absence of thoracic aortic endothelium. This inhibitory effect of paraoxon on vasoconstrictor-induced contraction was abolished in the absence of extracellular Ca2+, or in the presence of the Ca2+ channel inhibitor, verapamil. But atropine had little effect on the inhibitory effect of paraoxon on phenylephrine-induced contraction. Paraoxon also attenuated vascular smooth muscle contraction induced by the cumulative addition of CaCl2 and attenuated an increase of intracellular Ca2+ concentration induced by K+ in vascular smooth muscle cells. Moreover, paraoxon (30 microM) inhibited significantly L-type calcium current in isolated aortic smooth muscle cells of rabbits. In conclusion, our results demonstrate that paraoxon attenuates vasoconstrictor-induced contraction through inhibiting Ca2+ influx in the rabbits thoracic aorta.
authors.affiliation: Department of Pharmacology, Xiang-Ya Medical College, Central South University, Changsha, Hunan 410078, China.
authors.forename: Shouhong
authors.initials: S
authors.lastname: Zhou
authors.forename: Liying
authors.initials: L
authors.lastname: Liu
authors.forename: Xuhong
authors.initials: X
authors.lastname: Yang
authors.forename: Shujin
authors.initials: S
authors.lastname: Wu
authors.forename: Gengrong
authors.initials: G
authors.lastname: Chen
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D001013:Aorta, Thoracic / Q000187:drug effects* / Q000378:metabolism / Q000502:physiology; D002118:Calcium / Q000378:metabolism*; D020746:Calcium Channels, L-Type / Q000187:drug effects; D009119:Muscle Contraction / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000187:drug effects* / Q000378:metabolism / Q000502:physiology; D010261:Paraoxon / Q000494:pharmacology*; D018408:Patch-Clamp Techniques; D010656:Phenylephrine / Q000494:pharmacology; D011189:Potassium Chloride / Q000494:pharmacology; D011817:Rabbits; D014661:Vasoconstriction / Q000187:drug effects; D014662:Vasoconstrictor Agents / Q000494:pharmacology; D014664:Vasodilation / Q000187:drug effects; D014700:Verapamil / Q000494:pharmacology
chemical_list: D020746:Calcium Channels, L-Type; D014662:Vasoconstrictor Agents; D010656:Phenylephrine; D011189:Potassium Chloride; D014700:Verapamil; D010261:Paraoxon; D002118:Calcium
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