Molecular Mechanisms of Active Cross-bridge-dependent Regulation of Ca affinity of Cardiac Troponin

心肌肌钙蛋白 Ca 亲和力的主动跨桥依赖性调节的分子机制

基本信息

批准号：
10470010
负责人：
KURIHARA Satoshi
金额：
$ 4.03万
依托单位：
The Jikei University School of Medicine
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B).
财政年份：
1998
资助国家：
日本
起止时间：
1998 至 2000
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-10470010/
关键词：
cardiac muscle troponin Ca^<2+>muscle length cross-bridge Ca affinity Ca_<2+>

项目摘要

We investigated molecular mechanisms which regulate cardiac muscle contraction using intact and skinned preparations. We measured the Ca transients and tension using aequorin which was injected into superficial cells of ferret papillary muscles. A decrease in muscle length from Lmax to 88%Lmax transiently increased intracellular Ca concentration (extra-Ca) in accordance with tension reduction. The normalized extra-Ca to intracellular Ca concentration before length reduction was increased in the solution with low Ca concentration and was reduced at higher Ca concentrations. Bay K 8644 decreased the normalized extra-Ca. These results suggest that an increase in intracellular Ca concentration increases the number of attached cross-bridges and this increases the Ca affinity of troponin C, resulting in the small normalized extra-Ca. We also measured pCa-tension relation using Triton X-100-treated skinned preparations and observed the muscle length-dependent shift of the relation. pCa-tension relation was shifted to the left at longer muscle lengths (length effect). In the presence of higher concentrations of H ion and phosphate, Ca responsiveness was decreased but length effect was enhanced. Thus, attachment of the cross-bridges is a critical factor for length-dependent change in Ca affinity of cardiac troponin C.

我们研究了分子机制，这些机制通过完整和皮肤制剂来调节心肌收缩。我们使用注射到雪貂乳头状肌肉的表层细胞中测量了CA瞬变和张力。根据张力减少，肌肉长度从LMAX降低到88％LMAX瞬时增加了细胞内Ca浓度（Extrap-Ca）。在低Ca浓度的溶液中，在溶液中增加了归一化的外部Ca至细胞内Ca浓度，并在较高的Ca浓度下降低。 Bay K 8644降低了归一化的额外CA。这些结果表明，细胞内Ca浓度的增加增加了附着的跨桥的数量，这增加了肌钙蛋白C的Ca亲和力，从而导致小型归一化额外CA。我们还使用Triton X-100处理的皮肤制剂测量了PCA张力关系，并观察到了关系的肌肉长度依赖性移位。 PCA张力关系以较长的肌肉长度（长度效应）转移到左侧。在存在较高浓度的H离子和磷酸盐的情况下，Ca反应性降低，但长度效应得到了增强。因此，跨桥的附着是心脏肌钙蛋白C的Ca亲和力的长度依赖性变化的关键因素。