高盐饮食对大鼠离体胸主动脉环收缩功能的影响及其机制

高盐饮食对大鼠离体胸主动脉环收缩功能的影响及其机制 高盐饮食对大鼠离体胸主动脉环收缩功能的影响及其机制 【关键词】 高盐饮食 高血压 动脉环 平滑肌 Abstract: Objective: To investigate the effect of high-salt diet on the contraction of the rat‘s thoracic aorta and its mechanism. Methods: Twenty female SD rats were randomly divided into normal control (NC) group and high-salt (HS) group (n=10). After 2 weeks, the rats were anesthetized with chloral hydrate and their blood pressures were measured. Using the isolated rat‘s thoracic aorta ring perfusion model, the effect of phenylephrine (PE) on the thoracic aorta ring free of endothelia was observed. Firstly, the thoracic aorta ring without endothelia was pretreated with calcium-free liquid, then, it was contracted with PE. In this procedure, two groups‘ differences were observed. Thirdly, the release of intracellular calcium induced by 1，4，5-triphosphate inositol (IP3) was blocked using calcium-free liquid plus heparin and the path of diacylglycerol-protein kinase C (DG-PKC) was observed. Results: There were no significant difference in blood pressure in two groups. However, after the ring was pretreated with calcium-free liquid and then treated with PE, it was found that the contraction intension of the thoracic aorta ring in HS group was significantly higher than that in NC group (P0.01). Conclusion: Although the blood pressure in rats fed with high-salt diet is normal in the early stage, the vascular smooth muscle contraction excited by agonist has strengthened, which may be related to the increasing intracellular calcium, especially the increasing activity of the DG-PKC pathway. Key words: High-salt diet; hypertension; arterial ring; vascular smooth muscle 高盐饮食能使盐敏感者的血压升高,并且涉及血压调节的内分泌及生化代谢也都现异常，如钠代谢异常、肾脏潴钠倾向、交感神经系统调节缺陷等[1]。韩运峰等报道，高盐饮食能使感觉损伤性大鼠血压升高， 并伴有细胞内钙‎‎离子浓度升高。那么，在盐敏感性高血压发病过程中，血压还没有 升高的情况下，高盐饮食是否已经使血管平滑肌收缩功能发生异常,平滑肌细胞内的钙离子浓度是否升高,钙离子浓度升高是否会使血管平滑肌收缩功能发生异常,在这方面的研究未曾报道。本实验给SD大鼠高盐(4%氯化钠)饲料喂养2 w后,观察血压与血管张力的变化，并分析其可能的机制。 1 材料和方法 1.1 设备 离体血管环灌流装置、PowerLab生物功能实验系统(8-SP型， PowerLab ADInstruments公司生产，澳大利亚)。 1.2 药物与试剂 苯肾上腺素(phenylephrine，PE，上海禾丰制药有限公司生 产);乙酰胆碱(acetylcholine，Ach，上海试剂二厂生产);Kreb-Henseleit(K-H)液(mmol/L): NaCl 118.0 mmol/L，KCl 4.7 mmol/L，NaH2PO4 1.2 mmol/L，MgSO4?7H2O 1.2 mmol/L，CaCl2 2.5 mmol/L， glucose 11.0 mmol/L，NaHCO3 25.0 mmol/L;无钙液: NaCl 118.0 mmol/L，KCl 4.7 mmol/L，NaH2PO4 1.2 mmol/L，MgSO4?7H2O 1.2 mmol/L，EDTA 0.05 mmol/L，glucose 11.0 mmol/L，NaHCO3 25.0 mmol/L。 1.3 动物与分组 雌性SD大鼠体重200,220 g，购自温州医学院实验动物中心(浙医动字第220170002号)。实验随机分为2组: 正常饮食(NC)组和高盐(4%氯化钠)饮食(HS)组。NC组用普通的大鼠饲料喂养，HS组用普通大鼠饲料加入氯化钠以质量比配成4%的氯化钠饲料，喂养2 w后进行血压测量。 1.4 血压测量 用10%水合氯醛腹腔注射麻醉后，暴露左侧颈总动脉，颈动脉插管连接PowerLab八导生理记录仪，待血压稳定10 min后，记录血压值。 1.5 血管环制备及张力测定 动物放血后，迅速开胸，分离出胸主动脉，置于95% O2和5% CO2混合气预饱和的4 ? K-H液中。小心剔除血管周围结缔组织，剪成3,4 mm的血管环。用棉签磨擦血管环内表面去除内皮细胞，以制备内皮去除的血管环。将血管环悬挂于预置10 ml K-H液的浴槽内，37 ? 恒温，持续通以95% O2和5% CO2混合气体。血管环静息张力2 g，平衡60 min，期间每15 min换液一次。用6×10-2 mol/L的KCl重复刺激3次，以诱发血管的最大收缩幅度。待血管稳定后，用10-6mol/L PE收缩血管环达峰值，加入10-5 mol/L Ach检验血管内皮完整性。若加Ach后使PE预收缩的血管舒张在20%以下，可认为内皮去除，否则弃用。 实验用PowerLab生物功能实验系统记录血管环张力变化，以6×10-2 mol/L的KCl刺激引起的最大收缩幅度为，所得数据用百分比表示。 1.5.1 无钙液预处理血管环的作用: 用无钙液孵育去内皮的血管环10 min，再加入3×10-7 mol/L PE使血管收缩，观察各组收缩幅度的情况。 1.5.2 无钙液加肝素预处理血管环的作用: 用无钙液和5×10-2g/L肝素共同预处理内皮破坏的血管环20 min，然后用3×10-7 mol/L PE使血管收缩，观察NC组和HS组收缩幅度的情况。 1.6 统计学处理方法 采用t检验。