Sarcolemmal Sodium Permeability and Contractile Force of Guinea Pig Papillary Muscle: Effects of Germitrine
Sarcolemmal Sodium Permeability and Contractile Force of Guinea Pig Papillary Muscle: Effects of Germitrine
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豚鼠乳头肌肌膜钠渗透性和收缩力：Germitrine 的影响
DOI：
10.1161/01.res.40.1.90
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发表时间：
1977
影响因子：
20.1
通讯作者：
M. Reiter
中科院分区：
文献类型：
--
作者：
P. Honerjager;M. Reiter
豚鼠乳头状肌的动作电位暴露于西洋参生物碱吉米他林(2μM)后，伴随着长时间的后去极化(最大幅度为8 mV；衰减的半衰期为32秒；总持续时间为˜75秒)。这种后去极化中断了复极化的末期。在重复刺激(0.1-1.0赫兹；80 NM吉米特林)期间，连续动作电位后的后去极化被相加，导致高达10 mV的持续去极化。后除极可被河豚毒素(TTX)可逆地消除。在Germitine诱导的后去极化过程中或之后的不同时间诱发的测试收缩显示了一个阶段，在此阶段肌肉发展力量的能力暂时增强。这种正性肌力影响在条件性刺激后1分钟达到最大值，此后衰减的时间为后去极化的半衰期的4.8倍。它被TTX可逆地废除，并被二氢哇巴因(DHO)增强。我们的结论是：Germitine通过显著延长钠通透性成分而引起后除极，该成分由快钠通道介导，通常仅限于动作电位的前几毫秒。Germitine引起的肌膜钠通透性(PNA)选择性和持续性增加引起正性肌力作用，可能是由于细胞内积累Na+交换细胞外钙离子所致。
SUMMARY The action potential of guinea pig papillary muscle exposed to the ceveratrum alkaloid germitrine (2 μM) is followed by a long-lasting after-depolarization (maximal amplitude, 8 mV; half-time of decay, 32 seconds; total duration, ˜75 seconds). This after-depolarization interrupts the terminal phase of repolariza-tion. During repetitive stimulation (0.1-1.0 Hz; 80 nM germitrine) the after-depolarizations that follow consecutive action potentials are summed, causing persistent depolarization of up to 10 mV. The after-depolarization is reversibly abolished by tetro-dotoxin (TTX). Test contractions evoked at various times during or after the germitrine-induced after-depolarization reveal a phase during which the ability of the muscle to develop force is transiently increased. This positive inotropic influence reaches its maximum 1 minute after the conditioning stimulus and thereafter decays with a half-time 4.8 times longer than the half-time of decay of the after-depolarization. It is reversibly abolished by TTX and augmented by dihydro-ouabain (DHO). We conclude: Germitrine induces an after-depolarization by prolonging dramatically the Na permeability component which is mediated by the fast Na channels and normally restricted to the first few milliseconds of the action potential. The germitrine-induced selective and persistent increase of sarcolemmal sodium permeability (PNa) causes a positive inotropic effect, probably because intracellularly accumulating Na ions exchange for extracellular Ca ions.