EXCITATION-CONTRACTION COUPLING IN SMOOTH-MUSCLE CELLS OF RABBIT MAIN PULMONARY-ARTERY
EXCITATION-CONTRACTION COUPLING IN SMOOTH-MUSCLE CELLS OF RABBIT MAIN PULMONARY-ARTERY
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DOI：
10.1113/jphysiol.1977.sp011990
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发表时间：
1977-01-01
影响因子：
5.5
通讯作者：
SUZUKI, H
中科院分区：
文献类型：
--
作者：
CASTEELS, R;KITAMURA, K;SUZUKI, H
增加外部K浓度使主肺动脉平滑肌细胞去极化，并且对于[K]o的10倍变化，该去极化达到58 mV的最大斜率。诱导收缩的阈值去极化为4 mV，在[K] 0为59 mM时达到最大收缩。10-8 M和10-7诱导张力而不使细胞去极化，但在较高浓度下，去甲肾上腺素不仅诱发大的张力反应，而且以剂量依赖性方式使细胞去极化。去甲肾上腺素对肺动脉的作用通过用蔗糖代替NaCl而明显改变：细胞轻微超极化，张力反应大大降低。通过研究在其它实验条件下对去甲肾上腺素的张力反应，所述实验条件引起细胞的小的超极化，例如5 mM-[Ca]o、2.9mM-[K]o或小的去极化，例如11.9mM-[K]o，发现膜电位的轻微改变可对去甲肾上腺素反应产生重要影响。[Ca]o和[Na]o的同时降低降低了对所有去甲肾上腺素浓度的张力反应。[Na]o的减少比[Ca]o的减少发挥更大的抑制作用。在解释这些结果的变化的膜电位，钙的可用性，和一些外部钙和钠之间的竞争必须考虑。对Krebs溶液和无Ca溶液中不同浓度的去甲肾上腺素的作用的研究表明，浓度高达2.5 × 105的去甲肾上腺素可使细胞生长缓慢。10-7 M通过增加Ca内流引起收缩，而较高浓度也诱导细胞Ca的释放。咖啡因使细胞去极化并降低膜电阻。它以与去甲肾上腺素相同的方式改变K，Cl和Ca通量，但它抑制去甲肾上腺素诱导的机械反应。
Increasing the external K concentration depolarizes the smooth muscle cells of the main pulmonary artery, and this depolarization reaches a maximal slope of 58 mV for a 10-fold change of [K]o. The threshold depolarization for inducing contraction is at 4 mV and the maximal contraction is reached at a [K]o of 59 mM. Noradrenaline [norepinephrine] concentrations between 2 .times. 10-8 M and 10-7 induce tension without depolarizing the cells, but at higher concentrations noradrenaline not only elicits a large tension response but also depolarizes the cells in a dose-dependent way. The effect of noradrenaline on the pulmonary artery is appreciably modified by substituting sucrose for NaCl: the cells are slightly hyperpolarized and the tension response is very much reduced. By studying the tension response to noradrenaline in other experimental conditions which cause a small hyperpolarization of the cells, such as 5 mM-[Ca]o, 2.9 mM-[K]o or a small depolarization, such as 11.9 mM-[K]o, it was found that a slight modification of the membrane potential can exert an important effect on the noradrenaline response. A simultaneous decrease of [Ca]o and [Na]o reduces the tension response to all noradrenaline concentrations. A reduction of [Na]o exerts a more depressing effect than a reduction of [Ca]o. In interpreting these results changes of the membrane potential, availability of Ca, and some competition between external Ca and Na must be considered. A study of the effect of different concentrations of noradrenaline in Krebs solutions and Ca-free solution showed that concentrations up to 2.5 .times. 10-7 M elicit contraction by increasing the Ca influx, while higher concentrations also induce a release of cellular Ca. Caffeine depolarizes the cells and reduces the membrane resistance. It modifies the K, Cl and Ca fluxes in the same way as noradrenaline, but it suppresses the mechanical response induced by noradrenaline.