New Ca2+ agonist (Bay K 8644) enhances and induces cardiac slow action potentials.
New Ca2+ agonist (Bay K 8644) enhances and induces cardiac slow action potentials.
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新型 Ca2 激动剂 (Bay K 8644) 增强并诱导心脏慢动作电位。
DOI：
10.1152/ajpheart.1984.247.2.h337
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发表时间：
1984
期刊：
影响因子：
--
通讯作者：
Sperelakis,N
中科院分区：
文献类型：
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作者：
Wahler,GM;Sperelakis,N
Bay K 8644是硝苯地平的类似物，具有正性肌力和血管收缩作用，并被假定为Ca激动剂（即，Ca2+通道激活剂）。为了验证这一假设，我们研究了该化合物在离体豚鼠乳头肌中的电生理效应。Bay K 8644（10（-6）M）对正常的快动作电位几乎没有影响，尽管它确实增加了收缩性。然而，Bay K 8644确实诱导Ca2+依赖性慢动作电位（快Na+通道被25 mM K+灭活）。当预先用氯化四乙基铵（10 mM）加Ca 2+（4.0 mM）或异丙肾上腺素（2 × 10（-7）M）诱导慢动作电位时，10（-6）M Bay K 8644增强慢动作电位，即，增加其最大上升速率（Vmax），伴随其正性肌力作用。BayK8644的上述作用可被10（-6）M硝苯地平逆转。因此，Bay K 8644似乎增强了通过心肌慢通道的Ca2+内流，这与Bay K 8644是Ca2+通道刺激剂的概念一致。
Bay K 8644 is an analogue of nifedipine that has positive inotropic and vasoconstricting actions and was postulated to be a Ca agonist (i.e., a Ca2+-channel activator). To test this hypothesis, we examined the electrophysiological effects of this compound in isolated guinea pig papillary muscles. Bay K 8644 (10(-6) M) had little effect on the normal fast action potentials, although it did increase contractility. Bay K 8644 did, however, induce Ca2+-dependent slow action potentials (fast Na+ channels inactivated by 25 mM K+). When slow action potentials had been previously induced by tetraethylammonium chloride (10 mM) plus Ca2+ (4.0 mM) or isoproterenol (2 X 10(-7) M), 10(-6) M Bay K 8644 potentiated the slow action potentials, i.e., increased their maximal rate of rise (Vmax), concomitant with its positive inotropic effect. All effects of Bay K 8644 could be reversed by 10(-6) M nifedipine. Thus it appears that Bay K 8644 enhances Ca2+ influx through the myocardial slow channels, consistent with the concept that Bay K 8644 is a Ca2+-channel stimulator.