AT2受体对自发性高血压大鼠肾脏近曲小管上皮细胞AT1受体表达与功能的影响

Effect of AT_2 receptor on AT_1 receptor expression and function in epithelial cells of renal proximal tubule of spontaneously hypertensive rats

目的研究AT2受体激动剂CGP42112对自发性高血压大鼠(SHR)肾脏近曲小管上皮(RPT)细胞AT1受体的表达及功能的影响。方法以RPT细胞株作为研究对象,采用不同浓度AT2受体激动剂CGP42112(10-9～10-7 mol/L)作用24h或同一浓度CGP42112(10-7 mol/L)作用不同时间(8、16、24h),应用Western blotting和RT-PCR法检测AT1受体蛋白和mRNA表达的改变。采用CGP42112(10-7 mol/L)预先作用24h,观察其对血管紧张素Ⅱ(AngⅡ)作用下Na+-K+-ATP酶活性的影响;比较CGP42112(10-7mol/L)作用30min与作用24h后洗脱2h,Na+-K+-ATP酶活性的差异。结果 CGP42112作用于AT2受体后可明显抑制RPT细胞AT1受体蛋白的表达,且呈现一定的浓度与时间依赖性。CGP42112(10-7 mol/L)能够抑制AT1受体mRNA的表达水平。与AngⅡ单独作用比较,CGP42112(10-7 mol/L)预处理24h可使AngⅡ(10-11 mol/L)增强Na+-K+-ATP酶活性的效应明显降低。CGP42112(10-7 mol/L)作用30min后,Na+-K+-ATP酶活性显著降低;但作用24h洗脱后2h,Na+-K+-ATP酶活性与对照组比较无明显差异。结论 AT2受体能够抑制SHR大鼠RPT细胞AT1受体的表达及其介导的Na+-K+-ATP酶活性增强的效应。

Objective To examine the effect of AT2 receptor agonist CGP42112 on the expression and function of AT1 receptor in the epithelial cells of the renal proximal tubule（RPT） of spontaneously hypertensive rats（SHRs）.Methods The present study investigated RPT cell strains and adopted different concentrations of AT2 receptor agonist CGP42112（10-9mol/L to 10-7mol/L） to act for 24h or the same concentration of CGP42112（10-7mol/L） to act for different periods（8,16,and 24h）.The protein and mRNA expression of AT1 receptor were then determined by immunoblot and reverse transcriptase-polymerase chain reaction.CGP42112（10-7mol/L） was adopted to act for 24h in advance.Its effect on Na＋-K＋-ATPase activity under the action of angiotensin II was observed and compared with the difference in Na＋-K＋-ATPase activity after the action of CGP42112（10-7mol/L） for 30min and 2h post-elution after the 24h action.Results The action of CGP42112 on AT2 receptor prohibits the expression of AT1 receptor protein in the RPT cells and shows certain dependence between concentration and time.CGP42112（10-7mol/L） could prohibit the expression level of AT1 receptor protein.Compared with the single action of AngII,pretreatment by CGP42112（10-7mol/L） for 24h could reduce the ability of AngII（10-11mol/L） in boosting the activity of Na＋-K＋-ATPase.After the action of CGP42112（10-7mol/L） for 30min,Na＋-K＋-ATPase could be reduced.However,2h post-elution after the 24h action,the activity of Na＋-K＋-ATPase has no apparent difference with that of the contrast group.Conclusions AT2 receptor could prohibit the expression of AT1 receptor in the RPT cells of SHRs and could boost the activity of Na＋-K＋-ATPase mediated by AT1 receptor.