Effects of alpha-adrenergic stimulation on intracellular sodium activity and automaticity in canine Purkinje fibers.
Effects of alpha-adrenergic stimulation on intracellular sodium activity and automaticity in canine Purkinje fibers.
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α-肾上腺素能刺激对犬浦肯野纤维细胞内钠活性和自动性的影响。
DOI：
10.1161/01.res.66.2.416
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发表时间：
1990
影响因子：
20.1
通讯作者：
Rosen,MR
中科院分区：
文献类型：
--
作者：
Zaza,A;Kline,RP;Rosen,MR
大约60%的成年犬浦肯野纤维对α 1肾上腺素能刺激有反应，自律性降低。最近对分离的浦肯野肌细胞的研究表明，这种负性变时作用是由Na-K泵的α 1-肾上腺素能激活引起的。在这项研究中，我们评估了1）钠钾泵激活是否与成年犬浦肯野纤维中α 1-肾上腺素能刺激的负性变时效应相关，以及2）α-受体激动剂对泵的作用是直接的还是由细胞内钠活性（aNai）增加介导的。我们用钠选择性微电极测定了5 × 10 ~（-9）和5 × 10 ~（-8）M苯丙酮酸对aNaI的影响。苯肾上腺素降低自律性的八浦肯野纤维，而增加发生在其他三个。速率降低总是伴随着aNai的降低（-3.9 mM; p小于0.05），而在速率增加的纤维中，aNai没有变化。为了评价苯肾上腺素在无自律性变化的情况下的作用，在起搏过程中研究了10根浦肯野纤维。在六种纤维中存在aNai的明显减少（~ 2.8mM）;在其他四种纤维中没有观察到变化。哌唑嗪可阻断苯肾上腺素的作用，但普萘洛尔不能阻断。我们得出结论，α 1-肾上腺素能刺激减少aNai的效果与Na-K泵的激活一致。此外，α 1-肾上腺素能刺激的这种作用与其负性变时作用密切相关。
Approximately 60% of adult canine Purkinje fibers respond to alpha 1-adrenergic stimulation with a decrease in automaticity. Recent studies of disaggregated Purkinje myocytes have suggested that this negative chronotropic effect results from alpha 1-adrenergic activation of the Na-K pump. In this study we evaluated 1) whether Na-K pump activation is associated with the negative chronotropic effect of alpha 1-adrenergic stimulation in adult canine Purkinje fibers and 2) if the effect of alpha-agonists on the pump is direct or mediated by an increase in intracellular sodium activity (aNai). We used sodium selective microelectrodes to determine the effects of 5 x 10(-9) and 5 x 10(-8) M phenylephrine on aNai. Phenylephrine decreased automaticity in five of eight Purkinje fibers while an increase occurred in the other three. The rate decrease was always accompanied by a decrease in aNai (-3.9 mM; p less than 0.05), whereas in fibers showing an increase in rate, aNai was unchanged. To evaluate the effect of phenylephrine in the absence of changes in automaticity, 10 Purkinje fibers were studied during pacing. A clear-cut reduction in aNai (-2.8 mM) was present in six fibers; no change was seen in the other four. The effect of phenylephrine was blocked by prazosin but not by propranolol. We conclude that the effect of alpha 1-adrenergic stimulation to reduce aNai is consistent with activation of the Na-K pump. Moreover, this action of alpha 1-adrenergic stimulation is closely linked to its negative chronotropic effect.