Tsien R W, Bean B P, Hess P, Lansman J B, Nilius B, Nowycky M C
J Mol Cell Cardiol. 1986 Jul;18(7):691-710. doi: 10.1016/s0022-2828(86)80941-5.
Cardiac calcium channel activity is markedly increased by beta-adrenergic agents or calcium agonists such as Bay K 8644. The molecular mechanisms underlying these important modulatory effects have been studied with patch clamp techniques by several groups. This paper presents new experiments and reviews published evidence from fluctuation analysis of whole cell calcium current and unitary recordings of single calcium channel activity. Two different factors underlie the enhancement of calcium channel activity seen with beta-stimulation or cyclic AMP: (1) increased availability of calcium channels, expressed in whole cell recordings as an increase in the number of functional channels and in single channel recordings as an increase in the proportion of non-blank sweeps. (2) changes in opening probability, due to alteration of the fast kinetics of channel opening and closing. Both factors contribute to the beta-adrenergic enhancement in frog, rat, and guinea-pig ventricular cells although their quantitative importance is somewhat variable. Unlike beta-adrenergic agents, calcium agonists such as Bay K 8644 promote a mode of channel gating that is characterized by long openings and short closings, seen only rarely in control or with beta-stimulation.
β-肾上腺素能药物或钙激动剂（如Bay K 8644）可显著增加心脏钙通道活性。几个研究小组已采用膜片钳技术对这些重要调节作用的分子机制进行了研究。本文介绍了新的实验，并回顾了已发表的关于全细胞钙电流波动分析和单个钙通道活性单位记录的证据。β刺激或环磷酸腺苷（cAMP）导致钙通道活性增强有两个不同因素：（1）钙通道的可用性增加，在全细胞记录中表现为功能性通道数量增加，在单通道记录中表现为非空白扫描比例增加。（2）由于通道开放和关闭的快速动力学改变，导致开放概率发生变化。这两个因素都对青蛙、大鼠和豚鼠心室细胞中的β-肾上腺素能增强有作用，尽管它们的定量重要性有所不同。与β-肾上腺素能药物不同，钙激动剂如Bay K 8644促进一种通道门控模式，其特征是开放时间长而关闭时间短，在对照或β刺激时很少见到。
