哇巴因和氯化锂对单个嗜铬细胞胞质钙离子的作用。

The actions of ouabain and lithium chloride on cytosolic Ca2+ in single chromaffin cells.

作者信息

De la Fuente M T, Maroto R, Esquerro E, Sánchez-García P, García A G

机构信息

Departamento de Farmacología, Facultad de Medicina, Universidad Autónoma de Madrid, Spain.

出版信息

Eur J Pharmacol. 1996 Jun 13;306(1-3):219-26. doi: 10.1016/0014-2999(96)00191-4.

DOI:10.1016/0014-2999(96)00191-4

PMID:8813635

Abstract

The effects of ouabain, Li+ and veratridine on the concentration of cytosolic free Ca2+ ([Ca2+]i) were studied in single fura-2-loaded bovine adrenal chromaffin cells. Superfusion of cells with ouabain (10 microM for 60 min) caused only a delayed mild increase of the Ca2+]i, from around 0.1 microM to 0.2-0.3 microM; this increase was Nao(+)-dependent. Replacement of all NaCl of the Krebs-Hepes solution by LiCl (144 mM) produced a gradual increase of [Ca2+]i, which remained elevated at a stable plateau of 0.4-0.5 microM for 40-50 min. When ouabain (in the presence of normal Nao+) or Li+ (in the absence of Nao+) was given in Krebs-Hepes solution containing no Ca2+, the reintroduction of 2.5 mM Ca2+ produced a fast elevation of the [Ca2+]i. In the case of ouabain-treated cells, the [Ca2+]i curve exhibited an initial phasic component which inactivated to a tonic component. omega-Conotoxin MVIIC (3 microM) and R56865 (10 microM) inhibited the phasic but not the tonic component. Veratridine (30 microM) induced large [Ca2+]i oscillations. Both ouabain or Li+ abolished such oscillations. These results are compatible with ouabain causing elevation of [Ca2+]i in bovine chromaffin cells through a dual mechanism, i.e. cell depolarisation and slowing down of the Na(+)-Ca2+ exchanger of their plasmalemma. Through its binding to the Na+ site on the Na(+)-Ca2+ exchanger, Li+ ions generate powerful Cai2+ signals that might be relevant to its known effects on neurosecretory mechanisms.

摘要

在单个用fura - 2加载的牛肾上腺嗜铬细胞中，研究了哇巴因、Li⁺和藜芦定对胞质游离Ca²⁺浓度（[Ca²⁺]i）的影响。用哇巴因（10 μM，作用60分钟）对细胞进行灌流，仅引起[Ca²⁺]i延迟性轻度升高，从约0.1 μM升至0.2 - 0.3 μM；这种升高依赖于Naₒ⁺。用LiCl（144 mM）替代Krebs - Hepes溶液中的所有NaCl，使[Ca²⁺]i逐渐升高，并在0.4 - 0.5 μM的稳定平台期保持升高40 - 50分钟。当在不含Ca²⁺的Krebs - Hepes溶液中加入哇巴因（在正常Naₒ⁺存在下）或Li⁺（在无Naₒ⁺时）后，再加入2.5 mM Ca²⁺会使[Ca²⁺]i快速升高。对于用哇巴因处理的细胞，[Ca²⁺]i曲线呈现出一个初始的相位成分，该成分会失活为一个紧张性成分。ω - 芋螺毒素MVIIC（3 μM）和R56865（10 μM）抑制相位成分，但不抑制紧张性成分。藜芦定（30 μM）诱导[Ca²⁺]i大幅振荡。哇巴因或Li⁺均可消除这种振荡。这些结果与哇巴因通过双重机制导致牛嗜铬细胞中[Ca²⁺]i升高相符，即细胞去极化和其质膜上Na⁺ - Ca²⁺交换器的减慢。通过与Na⁺ - Ca²⁺交换器上的Na⁺位点结合，Li⁺离子产生强大的Ca²⁺信号，这可能与其对神经分泌机制的已知作用相关。