组胺对钾离子使其部分去极化的豚鼠乳头肌中钙依赖性电反应和机械反应的恢复作用。
Restoration by histamine of the calcium-dependent electrical and mechanical response in the guinea-pig papillary muscle partially depolarized by potassium.
作者信息
Inui J, Imamura H
出版信息
Naunyn Schmiedebergs Arch Pharmacol. 1976 Sep;294(3):261-9. doi: 10.1007/BF00508394.
Electrophysiological and mechanical effects of histamine were observed in guinea-pig papillary muscle which had been depolarized and rendered inexcitable by elevation of potassium concentration in Tyrode solution to 27 mM. 1. Histamine (3 X 10(-7) to 3 X 10(-5) M) restored the action potential and tension development. The amplitude of the action potential was increased by 31.6 mV/10-fold increase in extracellular Ca2+ concentration. Nifedipine (10(-6) M) abolished the electrical and mechanical responses which had been restored by histamine (10(-5) M) but TTX (10(-5) M) did not affect them. Reduction of the extracellular Na+ concentration to one half decreased the amplitude and the maximum rate of rise of the action potential restored by histamine (10(-5) M) while the peak tension was increased and an after-contraction occurred. 2. The maximum rate of rise and the amplitude of the action potential restored by histamine (10(-5) M) decreased with increase in stimulus frequency from 0.1-1.6 Hz. The peak tension decreased and then increased. The shape of the developed tension was also changed. In the presence of caffeine (1 mM), the only effect of an increase in stimulus frequency was a decrease in peak tension but the change in the shape of developed tension did not occur. 3. The electrical and mechanical responses restored by histamine (3 X 10(-6) or 10(-5) M) were depressed by metiamide (3 X 10(-6) M) but not by diphenhydramine (10(-5) M) or bufetolol (10(-6) M). 4. The electrical response restored by histamine (10(-6) or 10(-5) M) was enhanced by papaverine (10(-5) M) and depressed by N-methylimidazole (10 mM). It is concluded that histamine may enhance the slow inward Ca2+ current mediated by histamine H2-receptors and the adenylate cyclase system in ventricular muscle and that the positive inotropic action of histamine may be attributed to these mechanisms.
在将台氏液中钾离子浓度升高至27 mM从而使其去极化并失去兴奋性的豚鼠乳头肌中，观察了组胺的电生理和机械效应。1. 组胺（3×10⁻⁷至3×10⁻⁵ M）可恢复动作电位和张力发展。动作电位幅度随细胞外Ca²⁺浓度每增加10倍而增加31.6 mV。硝苯地平（10⁻⁶ M）可消除由组胺（10⁻⁵ M）恢复的电和机械反应，但TTX（10⁻⁵ M）对其无影响。将细胞外Na⁺浓度减半会降低由组胺（10⁻⁵ M）恢复的动作电位幅度和最大上升速率，同时峰值张力增加并出现后收缩。2. 由组胺（10⁻⁵ M）恢复的动作电位的最大上升速率和幅度随刺激频率从0.1 - 1.6 Hz增加而降低。峰值张力先降低后增加。所产生张力的形状也发生了变化。在存在咖啡因（1 mM）的情况下，刺激频率增加的唯一效应是峰值张力降低，但所产生张力的形状没有变化。3. 组胺（3×10⁻⁶或10⁻⁵ M）恢复的电和机械反应被甲硫咪胺（3×10⁻⁶ M）抑制，但不被苯海拉明（10⁻⁵ M）或丁呋洛尔（10⁻⁶ M）抑制。4. 组胺（10⁻⁶或10⁻⁵ M）恢复的电反应被罂粟碱（10⁻⁵ M）增强，被N - 甲基咪唑（10 mM）抑制。结论是组胺可能增强心室肌中由组胺H₂受体和腺苷酸环化酶系统介导的缓慢内向Ca²⁺电流，并且组胺的正性肌力作用可能归因于这些机制。
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