Vasorelaxation Effect of Gastrodin on Isolated Thoracic Aorta Rings of Rats

Objective： To study the effect of gastrodin on isolated thoracic aorta rings of rats and to investigate the potential mechanism. Methods： A perfusion model of isolated thoracic aorta rings of rats was applied. The effect of cumulative gastrodin （5, 50, 100,150, 200, and 250 μ mol/L） on endothelium-intact aorta rings was investigated. The same procedure was applied to observe the effect of gastrodin on endotheliumintact/denuded aorta rings pre-contracted with 10.8 mol/L phenylephrine hydrochloride （PE）. The aorta rings incubated by 200 mmol/L gastrodin in the Ca2＋-free （K-H） solution was contracted by using PE. The effect of 200 mmol/L gastrodin on endothelium-denuded aorta rings pre-contracted with 60 mmol/L KCI was also observed. Results： Compared with the denuded gastrodin group, the intact gastrodin group could significantly relax the PE-contracted aorta rings （P〈0.01）. In Ca2＋-free （K-H） solution KHS, the PE-induced contraction rate of aorta rings pre-incubated by gastrodin was 6.5%± 0.7%, which was significantly less than the control group （11.8% ± 0.9%, P〈0.01）. However, after 3 mmol/L CaCl2 was added, the Ca2＋-induced contraction in the gastrodin group （51.7% ±2.4%） was similar to that in the control group （49.8% ± 2.8%）. The contractile rate of rings in the KCI-contracted gastrodin group （96.3%± 0.6%） was not significantly different from that in the control group （96.8± 1.2%）. Conclusions： Gastrodin has the effect of vasorelaxation on isolated thoracic aorta rings of rats. The mechanism of the vasorelaxation of gastrodin may mainly work through the inhibition of inositol 1,4, 5-trisphosphosphate receptor on the sarcoplasmic reticulum of the arterial smooth muscle, which leads to the reduction of the Ca2. released from the sarcoplasmic reticulum.

Effects of Total Alkaloids in Buxus microphylla Leaves on Aorta Smooth Muscle of Rats and Their Mechanisms

Objective To investigate the effects of total alkaloids in Buxus microphylla leaves(ABML)on isolated rats thoracic aorta rings,and then to explore the possible mechanisms underlying the effects.Methods Thoracic aortas of Wistar rats were isolated,removed,and mounted onto an organ bath.The effects of ABML at different concentration on the contraction of isolated thoracic aorta rings(with and without endothelium)precontracted with KCl or PE were observed with organ bath technique.Dose-effect curves of CaCl2 were recorded by organ bath technique.The concentration of intracellular Ca 2+ ([Ca 2+ ]i)increased by PE,KCI,and caffeine in the presence of ABML was determined using Ca 2+ sensitive fluorescence indicator Fura-2/AM loaded thoracic aorta vascular smooth muscle (VSM)cells of rats.Results In aorta rings precontracted with PE and KCl,ABML produced concentration- dependent relaxation in both intact and denuded endothelium ring groups.There was no difference in the inhibition of contraction between the intact and denuded endothelium ring groups at the same concentration.Exposure of isolated thoracic aorta rings to ABML led to a significant reduction in the contracting response induced by CaCl2,and shifted the cumulative concentration-response curves to right.ABML could significantly inhibit the extracellular Ca 2+ influx induced by PE and KCl under[Ca 2+ ]0 of 1.5 mmol/L,with inhibitory ratios of 40.2%and 49.9%,respectively.In the case of Ca 2+ -free,ABML could significantly inhibit the intracellular Ca 2+ release induced by PE,with inhibitory ratio of 72.4%.Conclusion ABML relaxes thoracic aorta VSM cells by suppressing influx of extracellular Ca 2+ via voltage-dependent Ca 2+ channel and receptor-operated Ca 2+ channel.