降钙素基因相关肽对牛蛙和豚鼠心房肌细胞的电生理效应。

Electrophysiological effects of calcitonin gene-related peptide in bull-frog and guinea-pig atrial myocytes.

作者信息

Ono K, Giles W R

机构信息

Department of Medical Physiology, University of Calgary School of Medicine, Alberta, Canada.

出版信息

J Physiol. 1991 May;436:195-217. doi: 10.1113/jphysiol.1991.sp018546.

DOI:10.1113/jphysiol.1991.sp018546

PMID:1905755

原文链接:https://pmc.ncbi.nlm.nih.gov/articles/PMC1181501/

Abstract

Electrophysiological effects of calcitonin gene-related peptide (CGRP) on action potentials and corresponding transmembrane currents in single myocytes from bull-frog and guinea-pig atria were studied using a whole-cell voltage-clamp method. 2. CGRP at relatively low concentrations increased the height of the action potential plateau in a dose-dependent manner in both bull-frog and guinea-pig myocytes. In addition, in bull-frog cells CGRP accelerated the early phase of repolarization, thus shortening the overall duration of the action potential. In contrast, in guinea-pig myocytes CGRP prolonged the action potential duration at all concentrations that were studied. 3. Voltage-clamp measurements demonstrated that CGRP increased transmembrane calcium current (ICa) in guinea-pig myocytes without a significant change in its voltage dependence. The ED50 value for this effect on ICa was 1.28 +/- 0.55 X 10(-8) M (n = 4). The time course of the inactivation of ICa was not affected by CGRP. 4. CGRP increased the delayed rectifier K+ current (IK) at relatively low concentrations in bull-frog atria, whereas relatively high concentrations were needed to increase IK in guinea-pig myocytes. This effect was observed even after complete inhibition of ICa. 5. CGRP had no significant effect on the inwardly rectifying background K+ current, IK1, even at very high concentrations. 6. Comparison of the time course of ICa augmentation in bull-frog and guinea-pig myocytes revealed an important difference in the effect of CGRP in these two types of cells. CGRP at maximal concentrations increased ICa transiently in bull-frog myocytes, whereas this response was sustained in guinea-pig myocytes. Isoprenaline (Iso) induced sustained increase in ICa in both species. When ICa was fully activated by Iso, CGRP at high concentrations strongly inhibited ICa in the bull-frog, whereas it had little effect on ICa in guinea-pig myocytes. 7. Intracellular application of GTP gamma S (guanosine 5'-O-(3-thiotriphosphate) 10(-4) M) greatly potentiated the CGRP effect on ICa; in contrast, GDP beta S (guanosine 5'-O-(2-thiodiphosphate), 2 x 10(-3) M) partially inhibited the CGRP-induced augmentation of ICa. Taken together, these results indicate that the stimulation of ICa by CGRP is mediated by a GTP-binding protein. 8. The observed dose-dependent changes in ICa and IK in bull-frog and guinea-pig myocytes can explain the different patterns of CGRP-induced changes in action potential shape in these two myocyte preparations.

摘要

采用全细胞膜片钳技术研究了降钙素基因相关肽（CGRP）对牛蛙和豚鼠心房单个心肌细胞动作电位及相应跨膜电流的电生理效应。2. 相对低浓度的CGRP以剂量依赖方式增加了牛蛙和豚鼠心肌细胞动作电位平台期的高度。此外，在牛蛙细胞中，CGRP加速了复极化的早期阶段，从而缩短了动作电位的总时程。相反，在豚鼠心肌细胞中，在所研究的所有浓度下CGRP都延长了动作电位时程。3. 电压钳测量表明，CGRP增加了豚鼠心肌细胞的跨膜钙电流（ICa），而其电压依赖性无明显变化。对ICa产生这种作用的半数有效剂量（ED50）值为1.28±0.55×10⁻⁸ M（n = 4）。CGRP不影响ICa失活的时间进程。4. 在牛蛙心房中，相对低浓度的CGRP增加了延迟整流钾电流（IK），而在豚鼠心肌细胞中则需要相对高浓度才能增加IK。即使在ICa被完全抑制后仍观察到这种效应。5. 即使在非常高的浓度下，CGRP对内向整流背景钾电流IK1也无明显影响。6. 比较牛蛙和豚鼠心肌细胞中ICa增强的时间进程发现，CGRP在这两种类型细胞中的作用存在重要差异。最大浓度的CGRP使牛蛙心肌细胞中的ICa短暂增加，而在豚鼠心肌细胞中这种反应是持续的。异丙肾上腺素（Iso）在两种动物中均诱导ICa持续增加。当ICa被Iso完全激活时，高浓度的CGRP强烈抑制牛蛙中的ICa，而对豚鼠心肌细胞中的ICa影响很小。7. 细胞内应用10⁻⁴ M鸟苷5'-O-(3-硫代三磷酸)（GTPγS）极大地增强了CGRP对ICa的作用；相反，2×10⁻³ M鸟苷5'-O-(2-硫代二磷酸)（GDPβS）部分抑制了CGRP诱导的ICa增强。综上所述，这些结果表明CGRP对ICa的刺激是由一种GTP结合蛋白介导的。8. 在牛蛙和豚鼠心肌细胞中观察到的ICa和IK的剂量依赖性变化可以解释在这两种心肌细胞制剂中CGRP诱导的动作电位形状变化的不同模式。