Relationship between action potential, contraction-relaxation pattern, and intracellular Ca2+ transient in cardiomyocytes of dogs with chronic heart failure

Abnormalities of contractile function have been identified in cardiomyocytes isolated from failed human hearts and from hearts of animals with experimentally induced heart failure (HF). The mechanism(s) responsible for these functional abnormalities are not fully understood. In the present study, we examined the relationship between action potential duration, pattern of contraction and relaxation, and associated intracellular Ca²⁺ transients in single cardiomyocytes isolated from the left ventricle (LV) of dogs (n = 7) with HF produced by multiple sequential intracoronary microembolizations. Comparisons were made with LV cardiomyocytes isolated from normal dogs. Action potentials were measured in isolated LV cardiomyocytes by perforated patch clamp, Ca²⁺ transients by fluo 3 probe fluorescence, and cardiomyocyte contraction and relaxation by edge movement detector. HF cardiomyocytes exhibited an abnormal pattern of contraction and relaxation characterized by an attenuated initial twitch (spike) followed by a sustained contracture ('dome') of 1 to 8 s in duration and subsequent delayed relaxation. This pattern was more prominent at low stimulation rates (58% at 0.2 Hz, n = 211, 21% at 0.5 Hz, n = 185). Measurements of Ca²⁺ transients in HF cardiomyocytes at 0.2 Hz manifested a similar spike and dome configuration. The dome phase of both the contraction/relaxation pattern and Ca²⁺ transients seen in HF cardiomyocytes coincided with a sustained plateau of the action potential. Shortening of the action potential duration by administration of saxitoxin (100 nM) or lidocaine (30 μM) reduced the duration of the dome phase of both the contraction/relaxation profile as well as that of the Ca²⁺ transient profile. An increase of stimulation rate up to 1 Hz caused shortening of the action potential and disappearance of the spike-dome profile in the majority of HF cardiomyocytes. In HF cardiomyocytes, the action potential and Ca²⁺ transient duration were not significantly different from those measured in normal cells. However, the contraction-relaxation cycle was significantly longer in HF cells (314 ± 67 ms, n = 21, vs. 221 ± 38 ms, n = 46, mean ± SD), indicating impaired excitation-contraction uncou pling in HF cardiomyocytes. The results show that, in cardiomyocytes isolated from dogs with HF, contractile abnormalities and abnormalities of intracellular Ca²⁺ transients at low stimulation rates are characterized by a spike-dome configuration. This abnormal pattern appears to result from prolongation of the action potential. Received 22 January 1998; received after revision 16 March 1998; accepted 27 March 1998     

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Banach空间中一类非线性积分微分方程的解

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两粒子Boltzmann方程组的局部解的存在唯一性

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压缩映射原理的等价命题及其构造性证明

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家兔胃消化性运动及收缩波分类

对 21 只带有胃瘘管(重2.5克)的兔,用气球法记录胃运动;另5只兔装有十二指肠再返瘘管(重2.3克/对),以检测进食前后胃排空量的动态变化。结果表明:兔胃呈持续性运动,但有低潮期(持续几分到十几分钟),表现为紧张度低平,收缩波幅明显减小并偶有高波出现。胃收缩波型分三类:快节律波(即20秒节律波)、慢节律波和长周期紧张性收缩。进食后胃排空量增多,各类波特别是慢节律波中三种波的数量比例分别出现明显增大或减小,这提示在促进胃排空方面,几种波分别起着不同的作用。本文对兔胃运动波型的分类,不是完全按照传统标准——单纯根据形态,而是掺进了“功能”这一因素。     

寻找欧拉生成子图最大边数的一个方法

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用压缩映射原理证明较弱条件下的隐函数存在定理

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