摘要
目的:从在体和离体水平分别探讨L-精氨酸对病理性心肌肥厚的影响及相关机制。方法:(1)在体水平:将大鼠分为假手术组、手术组、L-精氨酸(L-arginine,L-Arg)组和L-硝基精氨酸甲酯(N-nitro-L-arginine methy lester,L-NAME)组(L-Arg+L-NAME组),利用腹主动脉缩窄制作大鼠模型。检测心肌内蛋白合成总量与心率、血压;比色法检测心肌内一氧化氮(NO)含量、放射免疫法检测心肌AT Ⅱ含量,RT-PCR检测心肌内血管紧张素转换酶(angiotensin converting enzyme,ACE)mRNA的表达水平。(2)离体水平:将原代培养的心肌细胞分为对照组、血管紧张素Ⅱ(AngiotensinⅡ,ATⅡ)处理组、L-Arg处理组(AT Ⅱ+L-Arg)及L-NAME处理组(ATⅡ+L-Arg+L-NAME)。RT-PCR检测原代培养心肌细胞诱导型一氧化氮合酶(inducible NO synthase,iNOS)、ATⅡ的1型受体(AT Ⅱreceptor type 1,ATR1)和2型受体(ATⅡ receptor type 2,ATR2)mRNA的表达水平;Western印迹法检测原代培养心肌细胞iNOS蛋白表达水平。结果:(1)L-Arg提高了腹主动脉缩窄大鼠心肌内NO含量,降低了心肌ATⅡ含量、心肌蛋白合成总量、左心室质量/体质量比值以及ACE mRNA的表达量;L-NAME可消除L-Arg的上述作用;(2)在离体条件下,与ATⅡ组相比,L-Arg处理组心肌细胞NO含量、iNOS mRNA及蛋白水平的表达量均有提高,ATR1 mRNA表达水平下降;L-NAME处理组与ATⅡ处理组就上述指标相比无显著性差异;各组细胞ATR2 mRNA表达水平无明显差异;(3)多元逐步回归分析显示心肌内蛋白合成总量与血压水平、心率之间均不存在回归关系,而心肌NO和ATⅡ含量则可作为心肌内蛋白合成总量的预测因子;(4)心肌内ATⅡ含量、ACE mRNA表达量及心肌细胞ATR1 mRNA表达量均与NO含量之间存在线形负相关关系。结论:(1)心肌肥厚的形成与心肌内NO、ATⅡ含量密切相关;(2)L-Arg通过增强心肌iNOS表达,致NO生成增加。NO可减少心肌内ATⅡ生成,并通过调控心肌ACE及ATR1表达来抑制病理性心肌肥厚的形成;(3)ATR2并未参与上述过程。
Objective：To evaluate the in vivo and in vitro effects of L-arginine （L-Arg） on cardiac hypertrophy and the re- lated mechanisms. Methods： （1） In vivo study, rats were divided into sham-operation group, operation group, L-arginine （L- Arg） group, and N-nitro-L-arginine methyl ester （L-NAME） group. Coaretation of abdominal aortic artery was performed in rats of the operation group, L-Arg group and L-NAME group. The total protein level in the heart, the heart rate and blood pressure were all determined; cardiac nitric oxide （NO） content was detected by colorimetric method ; cardiac ATⅡ content was determined by radioimmunoassay; and the expression of angiotensin converting enzyme （ACE） mRNA was determined by RTPCR. （2） In vitro study, primarily cultured cardiomyocytes were divided into control group, Angiotensin Ⅱ （AT Ⅱ ）-treated group, L-Arg treated group, and L-NAME treated group. RT-PCR was used to examine the mRNA expression of inducible NO synthase （iNOS）, AT Ⅱ receptor type 1 （ATR1） and ATR2; Western blotting as employed to examine the iNOS protein ex- pression. Results： （1） L-Arg increased the content of NO in animals of the operation group, decreased the content of ATⅡ , total protein synthesis, ratio of left ventricle mass/body mass, and expression of ACE mRNA; and L-NAME could block theabove effect of L-Arg. （2） Compared with ATⅡ group,ATⅡ ＋L-Arg higher content of NO, higher expression of iNOS mR- NA and protein, and lower ATR1 mRNA level; the above indices were similar between ATⅡ ＋L-Arg＋L-NAME group and ATⅡ group. The expression of ATR2 mRNA was not significantly different between all the groups. （3） Multiple stepwise regression analysis revealed no relationship of regression between total protein level with blood pressure level or the heart rate. Cardiac NO and ATⅡ contents could serve as predictors for total protein level in the heart. （4） Cardiac NO content was negatively correlated with the cardiac ATⅡ content and ACE and ATR1 expression level. Conehtsion： （1） The development of cardiac hypertrophy is closely related to cardiac NO and ATⅡ levels. （2） L-Arg can increase cardiac NO content through enhancing myocardial iNOS expression; NO can reduce ATⅡ production in myocardiocytes and can inhibit the formation of cardiac hypertrophy by reducing the expression of ACE and ATR1. （3） ATR2 does no participate in the above process.
出处
《第二军医大学学报》
CAS
CSCD
北大核心
2008年第2期177-183,共7页
Academic Journal of Second Military Medical University
