Determinants of hypoxic and posthypoxic myocardial contracture.
Determinants of hypoxic and posthypoxic myocardial contracture.
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缺氧和缺氧后心肌挛缩的决定因素。
DOI：
10.1152/ajpheart.1977.232.5.h526
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发表时间：
1977
期刊：
影响因子：
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通讯作者：
M. Weisfeldt
中科院分区：
文献类型：
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作者：
H. Greene;M. Weisfeldt
在等长收缩的大鼠心肌小梁和猫右心室乳头肌中研究了挛缩（在固定长度下静息张力升高）与收缩活动之间的关系。在29℃下用95%O₂ - 5%CO₂平衡的溶液中，处于Lmax的肌肉以12次/分钟的频率起搏。在大鼠心肌中，在碱性pH下暴露于缺氧（95%N₂ - 5%CO₂）60分钟会产生挛缩。在猫心肌中，暴露于洋地黄并从缺氧中恢复会导致挛缩。在这两种标本中，延迟松弛都不是静息张力升高的原因。在缺氧期间未起搏的肌肉中，尽管完全没有收缩活动，也会出现挛缩。暴露于低钙或酸中毒可逆转或阻止静息张力升高。因此，挛缩可以：1）是动态的、可逆的，并受影响细胞内钙可利用性的因素调节；2）与收缩活动以及松弛系统的明显活动无关；3）不同于延迟或不完全松弛。从缺氧中恢复期间挛缩的程度并非仅仅是缺氧期间收缩活动水平的函数，而似乎与关键时间的钙可利用性有关。
The relationship between contracture (a rise in resting tension at constant length) and contractile activity was studied in isometric rat trabeculae carneae and cat right ventricular papillary muscles. Muscles at Lmax were paced at 12/min in solutions equilibrated at 29 degrees C with 95% O2-5% CO2. In rat myocardium, exposure to 60 min hypoxia (95% N2-5% CO2) at alkalotic pH produced contracture. In cat myocardium contracture was produced by the combination of exposure to digitalis and the recovery from hypoxia. Delayed relaxation was not responsible for the rise in resting tension in either preparation. In muscles not paced during hypoxia, contracture appeared despite total absence of contractile activity. Exposure to low calcium or acidosis reversed or prevented the rise in resting tension. Thus, contracture can be: 1) dynamic, reversible, and modified by factors which affect intracellular calcium availability; 2) independent of contractile activity and apparent activity of the relaxing system; and 3) distinct from delayed or incomplete relaxation. The extent of contracture during the recovery from hypoxia is not simply the function of the level of contractile activity during hypoxia but appears related to calcium availability at a critical time.