褪黑素经MT受体介导在运动改善SHR动脉内皮功能中的作用
Role of MT in Exercise Improving Artery Endothelial Function in SHR by Receptor

摘要：目的：探讨褪黑素（melatonin, MT）在有氧运动改善自发性高血压大鼠（SHR）肠系膜动脉功能中的作用及可能的外周血管机制。方法：选用雄性SHR 16只，随机分为高血压安静组（SHR-SED）和高血压运动组（SHR-EX），后者进行8周有氧跑台运动。另选用同龄雄性WKY大鼠8只作为正常血压对照组。8周后，取肠系膜动脉，采用离体微血管环实验测定二级肠系膜动脉的舒缩特性、western blot和免疫荧光共染法检测肠系膜动脉的褪黑素受体MT1、MT2和eNOS蛋白的表达和分布。结果：1）SHR-SED组基础收缩压（SBP）显著高于WKY组，经过有氧运动训练后SBP显著下降；2）有氧运动可增加肠系膜动脉对乙酰胆碱（ACh）的舒张反应，其pIC50值为WKY>SHR-EX>SHR-SED； MT (10?4 mol/L)预孵育微血管环20 min，可明显增加ACh（10-9～10-5 mol/L）的舒张反应，但对外源一氧化氮供体硝普钠（SNP，10-9～10-5 mol/L）诱发的舒张反应无明显效果； 且MT1/MT2非选择性拮抗剂luzindole（2×10?6 mol/L）预孵育微血管环20 min，可阻断MT对ACh舒张反应的加强效果；3）SHR-EX组MT1、MT2和eNOS表达均显著高于SHE-SED组，有氧运动显著抑制MT1、MT2和eNOS表达的下调；4）免疫荧光共定位检测MT2蛋白位于整个肠系膜动脉内，包括细胞外膜、血管平滑肌细胞层和内皮细胞层，eNOS蛋白主要存在于肠系膜动脉的内皮细胞层，MT2和eNOS蛋白二者共定位于肠系膜动脉的内皮细胞层。结论：长期有氧运动可有效降低SHR的基础血压，增强肠系膜动脉血管舒张作用，其中褪黑素是其重要机制之一。褪黑素可能是通过血管褪黑素受体及内皮途径起作用。
Abstract: Objective: To investigate the role of melatonin (MT) in aerobic exercise improving mesenteric arterial function in spontaneously hypertensive rats (SHR) and its possible peripheral vascular mechanisms. Methods: Sixteen male SHR were randomly assigned to a sedentary control group (SHR-SED, n=8) and an exercise training group (SHR-EX, n=8) that underwent an 8-week motor treadmill training. Eight male WKY rats with the same age were used as normotensive control group. After 8 weeks, the mesenteric arteries were removed. The mechanical properties of small mesenteric arteries were tested by isolated vascular rings method. The protein expression and distribution of MT1/MT2 and eNOS were measured by Western blotting and Immunofluorescence staining. Results: 1) The basal systolic blood pressure (SBP) is higher in SHR-SED than in WKY, and it decreases after exercise. 2) Aerobic exercise can increase the relaxation responses of mesenteric artery to acetylcholine (ACh), the highest pIC50 value is WKY, followed by SHR-EX and SHR-SED. The 20 min MT (10?4 mol/L) preincubate vascular rings can increase relaxation responses induced by Ach (10-9~10-5 M), but cannot affect relaxation responses induced sodium nitroprusside (SNP, 10-9~10-5 M). The 20 min luzindole (2×10?6 mol/L) preincubate vascular rings can inhibit the effect of MT on ACh relaxation. 3) MT1, MT2 and eNOS expressions in SHR-SED are significantly higher than in SHE-SED, and exercise training attenuated the decrease expressions of MT1, MT2 and eNOS. 4) The results of Immunohistochemistry showed that MT2 is located in the whole mesenteric artery vessel wall (intima, media, adventitia), eNOS is mainly localized in the intimal endothelium layer of the mesenteric artery, MT2 with eNOS is located in the endothelial cell layer.