Constrictive effects of ethanolic extract of Fructus Aurantii on rat thoracic aorta and the underlying mechanisms

Aim To explore the constrictive effect of Fructus Aurantii extract(FAE) on rat thoracic aorta and the underlying mechanisms.Methods Isometric tension measurements were used to study the effect ofFructus Aurantii on isolated rat thoracic aorta rings.Laser scanning confocal microscope was employed to measure the concentration of intracellular free calcium.Results FAE caused a dose-dependent contraction of the rat isolated aorta rings with or without endothelium,and the constrictive effect of FAE was more stronger on endothelium-denuded aorta rings(74±4.9)% than on endothelium-intact aorta rings(44±3.4)%(P0.01).FAE induced contraction on the endothelium-intact rat aorta rings was increased by pretreatment with L-NAME(anitric oxide synthase inhibitor,300 μm·L-1),from(44±3.4)% to(77±5.3)%(P0.01).However,the constrictive effect of FAE was inhibited by pretreatment with Ca2+-free K-H solution or verapamil(an L-type calcium channel antagonist,10-5 mol·L-1),and the constrictive amplitude reduced by(52±3.8)% and(49±3.7)% respectively(P0.01).FAE also dose-dependently increased the intracellular free calcium concentration.Conclusions FAE exerted a dose-dependent vasoconstrictive effects on rat isolated aorta rings by opening the L-type voltage-dependent Ca2+ channels,and enhancing the extracellular Ca2+ influx.FAE might also stimulate the release of nitric oxide from endothelium cells,which partly compromised its vasoconstrictive effects.