Zobel Carsten, Zavidou-Saroti Persephone, Bölck Birgit, Brixius Klara, Reuter Hannes, Frank Konrad, Diedrichs Holger, Müller-Ehmsen Jochen, Bloch Wilhelm, Schwinger Robert H G
Laboratory of Muscle Research and Molecular Cardiology, Department of Internal Medicine III, University of Cologne, Joseph-Stelzmann-Str. 9, 50924, Cologne, Germany.
Eur J Appl Physiol. 2007 Jan;99(2):121-32. doi: 10.1007/s00421-006-0323-5. Epub 2006 Oct 25.
The present study aimed to characterize cardiac hypertrophy induced by activation of the renin-angiotensin system in terms of functional alterations on the level of the contractile proteins, employing transgenic rats harboring the mouse renin gene (TGR(mREN2)27). Ca2+-dependent tension and myosin ATPase activity were measured in skinned fiber preparations obtained from TGR(mREN2)27 and from age-matched Sprague-Dawley rats (SPDR). Western blots for troponin I (TnI) and troponin T (TnT) were performed and the phosphorylation status of TnI were evaluated in myocardial preparations. TnT and myosin heavy chain (MHC) isoforms were analyzed by RT-PCR. The pCa/tension relationship was shifted to the right in TGR(mREN2)27 compared to SPDR as indicated by increased Ca2+-concentrations required for half maximal activation of tension (SPDR 5.80, 95% confidence limits 5.77-5.82 vs. TGR(mREN2)27 5.69, 95% confidence limits 5.67-5.72, pCa units), while maximal developed tension was unaltered. Even more pronounced was the shift in the relationship between pCa and myosin-ATPase (SPDR 6.01, 95% confidence limits 5.99-6.03 vs. TGR(mREN2)27 5.77, 95% confidence limits 5.73-5.79, pCa units). The maximal myosin-ATPase activity was reduced in TGR(mREN2)27 compared to SPDR, respectively (211.0 +/- 28.77 micromol ADP/s vs. 271.6 +/- 43.66 micromol ADP/s, P < 0.05). Tension cost (ATPase activity/tension) was significantly reduced in TGR(mREN2)27. The beta-MHC expression was significantly increased in TGR(mREN2)27. There was no isoform shift for TnT (protein and mRNA), as well as TnI, and no alteration of the phosphorylation of TnI in TGR(mREN2)27 compared to SPRD. The present study demonstrates that cardiac hypertrophy, induced by an activation of the renin-angiotensin system, leads to adapting alterations on the level of the contractile filaments, which reduce tension cost.
本研究旨在利用携带小鼠肾素基因的转基因大鼠（TGR(mREN2)27），从收缩蛋白水平的功能改变方面，对肾素-血管紧张素系统激活所致的心脏肥大进行特征描述。在从TGR(mREN2)27和年龄匹配的Sprague-Dawley大鼠（SPDR）获取的去表皮纤维制剂中，测量了Ca2+依赖性张力和肌球蛋白ATP酶活性。对心肌制剂进行了肌钙蛋白I（TnI）和肌钙蛋白T（TnT）的蛋白质印迹分析，并评估了TnI的磷酸化状态。通过RT-PCR分析了TnT和肌球蛋白重链（MHC）亚型。与SPDR相比，TGR(mREN2)27的pCa/张力关系向右偏移，表现为张力半最大激活所需的Ca2+浓度增加（SPDR为5.80，95%置信区间为5.77 - 5.82；TGR(mREN2)27为5.69，95%置信区间为5.67 - 5.72，pCa单位），而最大发展张力未改变。pCa与肌球蛋白-ATP酶之间关系的偏移更为明显（SPDR为6.01，95%置信区间为5.99 - 6.03；TGR(mREN2)27为5.77，95%置信区间为5.73 - 5.79，pCa单位）。与SPDR相比，TGR(mREN2)27的最大肌球蛋白-ATP酶活性降低（分别为211.0±28.77微摩尔ADP/秒和271.6±43.66微摩尔ADP/秒，P<0.05）。TGR(mREN2)27的张力消耗（ATP酶活性/张力）显著降低。TGR(mREN2)27中β-MHC的表达显著增加。与SPRD相比，TGR(mREN2)27中TnT（蛋白质和mRNA）以及TnI没有亚型转换，且TnI的磷酸化没有改变。本研究表明，肾素-血管紧张素系统激活所致的心脏肥大导致收缩细丝水平的适应性改变，从而降低张力消耗。
