The relationship between acetylcholine-evoked Ca2+-dependent current and the Ca2+ concentrations in the cytosol and the lumen of the endoplasmic reticulum in pancreatic acinar cells
The relationship between acetylcholine-evoked Ca2+-dependent current and the Ca2+ concentrations in the cytosol and the lumen of the endoplasmic reticulum in pancreatic acinar cells
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DOI：
10.1007/s004240051103
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发表时间：
1999-11-01
影响因子：
4.5
通讯作者：
Petersen, OH
中科院分区：
文献类型：
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作者：
Park, MK;Tepikin, AV;Petersen, OH
在离体小鼠胰腺腺泡细胞的研究中，我们使用膜片钳全细胞记录配置来监测Ca 2+依赖性内向离子电流，并使用适当的Ca 2+敏感的荧光探针同时测量胞质溶胶（[Ca 2 +]（i））或内质网腔（[Ca 2 +]（Lu））中的Ca 2+浓度。高浓度的乙酰胆碱（ACh，10 μ M）引起[Ca ~（2+）]（i）增加，引起Ca ~（2+）依赖性内向电流激活。持续给予ACh数分钟后，内向电流和[Ca ~（2+）]（i）反应均明显降低，持续刺激ACh 4-10分钟后，内向电流反应消失，[Ca ~（2+）]（i）恢复到刺激前水平。用ACh（10 μ M）的短脉冲重复刺激导致内向电流和[Ca 2 +]（i）上升幅度下降的反应。ACh激活的内向电流完全依赖于[Ca ~（2+）]（i）的升高，但在[Ca ~（2+）]（i）较高时，电流达到饱和。ACh引起内质网腔中Ca ~（2+）的快速释放，在停止刺激后，[Ca ~（2+）]（Lu）仅非常缓慢地（10-15 min）完全恢复到刺激前水平。ACh的重复应用不改变钙依赖性电流与[Ca ~（2+）]（i）或电流与[Ca ~（2+）]（Lu）之间的关系。当[Ca ~（2+）]（Lu）大于100 μ M时，ACh诱发的Ca ~（2+）从存储器中释放的量很大，以致于电流响应最初是饱和的。我们的结论是乙酰胆碱诱发的电流反应基本上取决于存储的Ca 2+的释放。脱敏主要是由于细胞内钙库的再加载相对缓慢。
In a study of isolated mouse pancreatic acinar cells, we used the patch-clamp whole-cell recording configuration to monitor the Ca2+-dependent inward ionic current and simultaneously measured the Ca2+ concentration in either the cytosol ([Ca2+](i)) or the lumen of the endoplasmic reticulum ([Ca2+](Lu)), using appropriate Ca2+-sensitive fluorescent probes. A high concentration of acetylcholine (ACh, 10 mu M) evoked an increase in [Ca2+](i), which resulted in the activation of Ca2+-dependent inward current. Continued ACh application for several minutes led to a marked reduction in both the current and the [Ca2+](i) response and after about 4-10 min of sustained ACh stimulation, the inward current response had disappeared and [Ca2+](i) was back to the pre-stimulation level. Repeated stimulation with shorter pulses of ACh (10 mu M) resulted in responses of declining magnitude both in terms of inward current and [Ca2+](i) rises. The ACh-activated inward current was entirely dependent on the elevation of [Ca2+](i) but at a relatively high [Ca2+](i) the current: was saturated. ACh caused a rapid release of Ca2+ from the lumen of the endoplasmic reticulum and after discontinuation of stimulation, [Ca2+](Lu) was only very slowly (10-15 min) fully restored to the pre-stimulation level. Repeated applications of ACh did not change the relationships between the Ca2+-dependent current and [Ca2+](i) or the current and [Ca2+](Lu). When [Ca2+](Lu) was greater than 100 mu M, the ACh-evoked Ca2+ release from the store was so large that the current response was initially saturated. We conclude that the ACh-evoked current response essentially depends on the release of stored Ca2+. Desensitization is mainly due to the relatively slow reloading of the intracellular stores with Ca2+.