细胞外钾对兔心房小梁慢反应兴奋性的影响。

Effects of extracellular potassium on slow response excitability in rabbit atrial trabeculae.

作者信息

Cukierman S

出版信息

Cardiovasc Res. 1985 Dec;19(12):754-61. doi: 10.1093/cvr/19.12.754.

DOI:10.1093/cvr/19.12.754

Abstract

Small trabeculae were excised from the rabbit left atrium and exposed to 1 mmol . litre-1 Ba2+-Tyrode solution containing variable amounts of potassium (range: 10 to 25 mmol . litre-1). One end of the trabecula was stimulated by means of a suction electrode. Intracellular microelectrodes were employed for measuring membrane potentials. In presence of Ba2+, the cell depolarises and slow responses can be elicited. Slow responses thus obtained do not propagate. Slow response overshoot, maximum rate of rise and duration are depressed by increasing extracellular potassium concentrations ([K+]o). The resting potential decreases by 1 to 3 mV on changing [K+]o from 10 to 25 mmol . litre-1. The depression in slow response overshoot caused by [K+]o is compatible with an increase in the relationship between K+ and Ca2+ permeabilities as [K+]o increases. The dependence of slow response excitability on the frequency of stimulation is also depressed by [K+]o. The inhibition of slow response electrogenesis caused by extracellular potassium is an important phenomenon to consider in trying to understand the origin of certain cardiac arrhythmias.

摘要

从小兔左心房切下小梁，将其置于含不同钾浓度（范围：10至25 mmol·L⁻¹）的1 mmol·L⁻¹ Ba²⁺ - 台氏液中。小梁的一端用吸力电极刺激。采用细胞内微电极测量膜电位。在Ba²⁺存在的情况下，细胞发生去极化并可引发慢反应。如此获得的慢反应不传播。随着细胞外钾浓度（[K⁺]o）增加，慢反应超射、最大上升速率和持续时间降低。当[K⁺]o从10 mmol·L⁻¹变为25 mmol·L⁻¹时，静息电位降低1至3 mV。[K⁺]o引起的慢反应超射降低与随着[K⁺]o增加K⁺与Ca²⁺通透性之间关系的增加相一致。[K⁺]o也降低慢反应兴奋性对刺激频率的依赖性。细胞外钾引起的慢反应电活动抑制是试图理解某些心律失常起源时需要考虑的一个重要现象。