Force-calcium relationship depends on myosin heavy chain and troponin isoforms in rat diaphragm muscle fibers
Force-calcium relationship depends on myosin heavy chain and troponin isoforms in rat diaphragm muscle fibers
复制标题
DOI：
10.1152/jappl.1999.87.5.1894
复制
发表时间：
1999-11-01
影响因子：
3.3
通讯作者：
Sieck, GC
中科院分区：
文献类型：
--
作者：
Geiger, PC;Cody, MJ;Sieck, GC
本研究探讨了Ca 2+的敏感性膈肌（直径）纤维表达不同的肌球蛋白重链（MHC）亚型。我们假设表达MHC慢亚型的Dia纤维比表达MHC快亚型的Dia纤维具有更高的Ca 2+敏感性，并且这种Ca 2+敏感性的纤维类型差异反映了肌钙蛋白（Tn）复合物（TnC、TnT和TnI）的亚型组成。在单一Triton-X透化的Dia纤维中进行研究。测定每根纤维产生50%最大力时的Ca 2+浓度（pCa（50））。SDS-PAGE和Western分析用于确定单个纤维的MHC和Tn同种型组成。表达慢MHC亚型的Dia纤维的pCa（50）显著大于表达快MHC亚型的Dia纤维的pCa（50），并且这种更大的Ca 2+敏感性与Tn复合体的慢亚型的表达相关。然而，一些Dia纤维表达MHC，I，含有快速TnC同种型。这些结果表明，TnT，TnI，和TnC亚型的组合可能决定Ca 2+的敏感性在直径（m）纤维。
The present study examined Ca2+ sensitivity of diaphragm muscle (Dia,) fibers expressing different myosin heavy chain (MHC) isoforms. We hypothesized that Dia, fibers expressing the MHCslow isoform have greater Ca2+ sensitivity than fibers expressing fast MHC isoforms and that this fiber-type difference in Ca2+ sensitivity reflects the isoform composition of the troponin (Tn) complex (TnC, TnT, and TnI). Studies were performed in single Triton-X-permeabilized Dia, fibers. The Ca2+ concentration at which 50% maximal force was generated (pCa(50)) was determined for each fiber. SDS-PAGE and Western analyses were used to determine the MHC and Tn isoform composition of single fibers. The pCa(50) for Dia, fibers expressing MHCslow was significantly greater than that of fibers expressing fast MHC isoforms, and this greater Ca2+ sensitivity was associated with expression of slow isoforms of the Tn complex. However, some Dia, fibers expressing MHC,I,, contained the fast TnC isoform. These results suggest that the combination of TnT, TnI, and TnC isoforms may determine Ca2+ sensitivity in Dia(m) fibers.