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首页> 外文期刊>American Journal of Physiology >Rapid exchange of actin-bound nucleotide in perfused rat heart.
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Rapid exchange of actin-bound nucleotide in perfused rat heart.

机译：灌注大鼠心脏中肌动蛋白结合核苷酸的快速交换。

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In the rat heart the actin-bound nucleotide contained both ATP and ADP. The ratio of bound ATP to bound ADP depended on the functional state of the heart; it was higher in hearts stopped reversibly in diastole (low Ca(2+), high Mg(2+), or high K(+)), than in stimulated (inotropic agents or pacing) hearts. Immunoblotting and gel electrophoresis showed the existence of G-actin (30% of total actin) in the cytoplasm of the heart. Pure actin was isolated from rat hearts: in G-actin the bound nucleotide readily exchanged with ATP or ADP, and in F-actin the bound nucleotide did not exchange with ATP or ADP. The free and bound nucleotides were separated in the intact heart by extraction with 75% methanol at -15 degrees C. In rat hearts perfused with (32)P-labeled orthophosphate the actin-bound nucleotide rapidly exchanged with the cytoplasmic ATP. The full exchange of the bound ATP was immediate, whereas the full exchange of the bound ADP was slower. The full exchange of the bound ATP was independent of the heartbeat frequency, whereas the full exchange of the bound ADP was frequency dependent. The data suggest that the transformation of actin monomer-ATP to actin polymer-ADP is a part of the normal contraction-relaxation cycle of the rat heart.
机译：在大鼠心脏中，肌动蛋白结合的核苷酸同时含有ATP和ADP。结合的ATP与结合的ADP的比例取决于心脏的功能状态。在心脏舒张期（低Ca（2+），高Mg（2+）或高K（+））中可逆停止的心脏中，其发生率高于受激（正性肌力药或起搏器）心脏。免疫印迹和凝胶电泳显示，心脏细胞质中存在G-肌动蛋白（占总肌动蛋白的30％）。从大鼠心脏中分离出纯肌动蛋白：在G-肌动蛋白中，结合的核苷酸易于与ATP或ADP交换，而在F-肌动蛋白中，结合的核苷酸不与ATP或ADP交换。通过在-15摄氏度下用75％甲醇提取，在完整的心脏中分离出游离和结合的核苷酸。在大鼠心脏中，灌注有（32）P标记的正磷酸盐，与肌动蛋白结合的核苷酸迅速与细胞质ATP交换。结合的ATP的完全交换是立即的，而结合的ADP的完全交换较慢。结合的ATP的完全交换与心跳频率无关，而结合的ADP的完全交换与频率有关。数据表明肌动蛋白单体-ATP向肌动蛋白聚合物-ADP的转化是大鼠心脏正常松弛松弛周期的一部分。

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