慢性肾衰大鼠血管平滑肌上钙激活钾通道功能的改变

The Function Alterations of Calcium-activated Potassium Channel in Aortic Smooth Muscle of Chronic Renal Failure Rats

目的:研究慢性肾衰时,大鼠血管平滑肌上钙激活钾(KCa)通道功能的变化。方法:将40只SD大鼠随机分为假手术组、病理6周组、病理10周组和病理14周组。对各病理组大鼠进行5/6肾切除致慢性肾衰,分别测定各组大鼠血清生化指标和尿蛋白水平,对其胸主动脉环进行血管张力反应性测定,并对胸主动脉KCa通道mRNA进行实时荧光定量PCR检测。结果:血生化和尿蛋白指标显示慢性肾衰造模成功。血管张力反应性测定中,各病理组在无药物干预条件下,由乙酰胆碱引起的舒张功能均较假手术组明显减弱(P<0.01);通过L-硝基-精氨酸甲酯(L-NAME)、吲哚美辛和KCa通道阻滞剂进行不同干预后发现,各病理组KCa通道功能均有所下降,导致血管舒张功能紊乱。病理组间比较显示,在L-NAME单独干预及L-NAME与吲哚美辛共同干预两种条件下,病理10周组血管最大舒张程度均明显低于病理6周组(P<0.05),而病理10周组与病理14周组间差异不大。PCR反应显示,与假手术组相比,各病理组KCa通道代表基因KCNMA1和KCNN2表达量均下降,但仅后者有极显著性差异(P<0.01)。各病理组间KCNMA1和KCNN2表达量均无显著性差异。结论:慢性肾衰会造成大鼠血管平滑肌KCa通道正常功能的改变,从而导致血管舒张功能受到损伤,损伤作用加重至10周时趋于稳定;慢性肾衰时血管平滑肌KCa通道mRNA表达的抑制作用未表现出有增龄变化。

Objective：To investigate the function alterations of calcium-activated potassium channel in aortic smooth muscle of chronic renal failure rats.Methods：Forty SD rats were randomly devided into sham-operated group,5/6 nephrectomy（5/6NX） for 6 weeks（5/6NX-6W） group,5/6NX-10W group and 5/6NX-14W group.The chronic renal failure models were established on rats by 5/6NX.The influence of chronic renal failure on rat model was confirmed by detecting the serum biochemicals and urine protein,and the relaxation of thoracic aortas was detected under different intervention conditions.Expression of KCa channel mRNA was also examined by real-time quantitative PCR.Results：Plasma concentrations of urea nitrogen,creatinine,total potassium and the total urine protein in all the NX groups were higher than those in the sham-operated group which indicated that the chronic renal failure model was formed.Compared with the sham-operated group,the relaxation induced by acetylcholine decreased obviously among all the NX groups（P0.01）.The experiment with L-nitro-arginine-methyl-ester（L-NAME）,indomethacin,and apamin＋iberiotoxin suggested that the KCa channel was deficient after NX,leading to the functional disorder of endothelium-dependent relaxation.It is shown that under the interfering effect of L-NAME or L-NAME＋indomethacin,the relaxtion degree of 5/6NX-10W group was obviously lower than that of the 5/6NX-6W group（P0.05）,while there was no significant difference between the 5/6NX-10W group and the 5/6NX-14W group.The PCR results showed that the mRNA expression of KCa channel was diminished in all the NX groups compared with sham-operated group,but only the change of KCNN2 expression was significant（P0.01）.No significant difference was observed on the mRNA expression levels of either KCNMA1 or KCNN2 among the several NX groups.Conclusion：The chronic renal failure caused function alterations of KCa channel on the aortic smooth muscles,leading to the relaxation abnormality of the thoracic aortas.The relaxation alteration was aggravated until the 10th week,while no such aggravation was observed on the mRNA expression of KCa channel.