Paraoxon Attenuates Vascular SmoothMuscle Contraction through Inhibiting Ca2+ Influx in the Rabbit Thoracic Aorta

Shouhong Zhou^1,2, Liying Liu¹, Xuhong Yang¹, ShujinWu1, and Gengrong Chen¹

1Department of Pharmacology, Xiang-Ya Medical College, Central South University, Changsha, Hunan 410078, China

2Department of Physiology, School of Medicine, University of South China, Hengyang, Hunan 421001, China

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 μM) attenuated thoracic aorta contraction induced by phenylephrine (1 μM) and/or a high K⁺ environment (80mM) 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 μM) 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.

Key Word : Paraoxon, Vascular SmoothMuscle Contraction, Ca²⁺ Influx, Rabbit Thoracic Aorta, organ baths in thoracic aortic rings, phenylephrine, high K⁺ environment, thoracic aortic endothelium

Sumber : Journal of Biomedicine and Biotechnology, Vol. 2010

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