Expression of slow skeletal troponin I in adult transgenic mouse heart muscle reduces the force decline observed during acidic conditions
Expression of slow skeletal troponin I in adult transgenic mouse heart muscle reduces the force decline observed during acidic conditions
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DOI：
10.1111/j.1469-7793.2001.00863.x
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发表时间：
2001-11-01
影响因子：
5.5
通讯作者：
Solaro, RJ
中科院分区：
文献类型：
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作者：
Wolska, BM;Vijayan, K;Solaro, RJ
1.心肌酸中毒与发育力下降有关。我们推测，在新生儿心脏中表达的缓慢骨骼肌钙蛋白I(SsTnI)是观察到的对酸性条件反应减弱的原因。为了直接验证这一假设，我们使用了在心脏中表达ssTnI的成年转基因(TG)小鼠。在这些小鼠中，心脏TnI(CTnI)完全被带有标志表位的ssTnI所取代(Tg-ssTnI*)，或者没有标志表位(Tg-ssTnI)。同时产生表达cTnI的Tg小鼠作为对照Tg系(Tg-cTnI)。以非转基因(NTG)窝产仔为对照。我们测量了在pH值为7.0和6.5时，所有四组左心室乳头肌经洗涤剂提取的纤维束的力-钙关系。NTG和Tg-cTnI小鼠心脏纤维束的力-钙关系相同，因此NTG小鼠作为Tg-ssTnI*和Tg-sTnI小鼠的对照。与NTG对照组相比，表达ssTnI的转基因小鼠的纤维束产生的力对钙离子更敏感。在TG心脏分离的纤维束中，由酸性pH引起的EC50(产生半最大力的钙离子浓度)的漂移明显小于NTG心脏。然而，Tg-ssTnI*组和Tg-ssTnI组的心脏之间的力-钙关系没有差异。我们还分离了表达ssTnI的NTG和TG小鼠右室乳头肌，并在细胞外pH 7.33和6.75下测量了等长力。在酸性pH条件下，NTG乳头肌的收缩力经一段时间的下降后恢复到60+/-3%(n=7)，TG-ss TnI*的收缩力达98+/-2%(n=5)，TG-ssTnI心脏的收缩力达96+/-3%(n=7)。我们的结果表明，TnI亚型组成在决定心肌力对酸中毒的敏感性方面起着至关重要的作用。
1. Acidosis in cardiac muscle is associated with a decrease in developed force. We hypothesized that slow skeletal troponin I (ssTnI), which is expressed in neonatal hearts, is responsible for the observed decreased response to acidic conditions. To test this hypothesis directly, we used adult transgenic (TG) mice that express ssTnI in the heart. Cardiac TnI (cTnI) was completely replaced by ssTnI either with a FLAG epitope introduced into the N-terminus (TG-ssTnI*) or without the epitope (TG-ssTnI) in these mice. TG mice that express cTnI were also generated as a control TG line (TG-cTnI). Non-transgenic (NTG) littermates were used as controls.2. We measured the force-calcium relationship in all four groups at pH7.0 and pH6.5 in detergent-extracted fibre bundles prepared from left ventricular papillary muscles. The force-calcium relationship was identical in fibre bundles from NTG and TG-cTnI mouse hearts, therefore NTG mice served as controls for TG-ssTnI* and TG-ssTnI mice. Compared to NTG controls, the force generated by fibre bundles from TG mice expressing ssTnI was more sensitive to Ca2+. The shift in EC50 (the concentration of Ca2+ at which half-maximal force is generated) caused by acidic pH was significantly smaller in fibre bundles isolated from TG hearts compared to those from NTG hearts. However, there was no difference in the force-calcium relationship between hearts from the TG-ssTnI* and TG-ssTnI groups.3. We also isolated papillary muscles from the right ventricle of NTG and TG mouse hearts expressing ssTnI and measured isometric force at extracellular pH 7.33 and pH 6.75. At acidic pH, after an initial decline, twitch force recovered to 60 +/- 3 % (n = 7) in NTG papillary muscles, 98 +/- 2% (n = 5) in muscles from TG-ssTnI* and 96 +/- 3 % (n = 7) in muscles from TG-ssTnI hearts. Our results indicate that TnI isoform composition plays a crucial role in the determination of myocardial force sensitivity to acidosis.