Pepsinogen secretion:: coupling of exocytosis visualized by video microscopy and [Ca2+]i in single cells
Pepsinogen secretion:: coupling of exocytosis visualized by video microscopy and [Ca2+]i in single cells
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DOI：
10.1152/ajpgi.1998.274.6.g1166
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发表时间：
1998-06-01
影响因子：
4.5
通讯作者：
Kajiyama, G
中科院分区：
文献类型：
--
作者：
Tao, C;Yamamoto, M;Kajiyama, G
胃蛋白酶原分泌的常规体外研究已经测量了大量培养基中的分泌，并证明了Ca 2+在该过程中的关键作用。本研究进行，以获得更多的细节的分泌过程中，其关系到Ca 2+的变化在很短的时间内。用荧光Ca ~（2+）指示剂Fura ~ 2测定细胞内Ca ~（2+）（[Ca ~（2+）]（i）），用视频显微镜分析系统测定单个细胞的胞吐，研究了牛蛙消化细胞Ca ~（2+）动员与胞吐的关系。蛙皮素（3.2 × 10（-7）M）和氨甲酰甲胆碱（3.2 × 10（-4）M）引起[Ca 2 +]（i）（初始峰）的快速增加和相应的初始胞吐的高频率。在初始峰值之后，[Ca 2 +]（i）维持在比基线稍高的水平（持续阶段），具有相应的低频率胞吐。[Ca ~（2+）]（i）升高的持续期和相关的胞吐作用均通过细胞外Ca ~（2+）的耗竭而消除。低浓度的蛙皮素（3.2 × 10（-10）M）和氨甲酰甲胆碱（3.2 × 10（-7）M）引起持续的低振幅Ca 2+振荡，频率相应较低，但也引起持续的胞吐作用。这些数据表明：1）细胞反应在高浓度和低浓度的刺激之间是不同的，2）[Ca ~（2+）]（i）和胞吐之间有密切的关系，3）胞吐在[Ca ~（2+）]（i）升高14-45 s之后（n = 6），4）峰值[Ca ~（2+）]（i）和胞吐数量之间有显著的正相关。
Conventional in vitro studies of pepsinogen secretion have measured secretion into the bulk medium and have demonstrated the critical role of Ca2+ in the process. The present study was undertaken to obtain further details of the process of secretion and its relation to Ca2+ changes over very short time periods. The relation between Ca2+ mobilization and exocytosis in an isolated individual peptic cell of the bullfrog was investigated by a method to measure both intracellular Ca2+ ([Ca2+](i)), using a fluorescent Ca2+ indicator, fura 2, and exocytosis from single cells using a video microscope analyzing system. Bombesin (3.2 x 10(-7) M) and bethanechol (3.2 x 10(-4) M) caused a rapid increase in [Ca2+](i) (initial peak) and a corresponding high frequency of initial exocytosis. After the initial peak, [Ca2+](i) was maintained at a somewhat elevated level over the baseline (sustained phase), with a corresponding low frequency of exocytosis. Both the sustained phase of elevated [Ca2+](i) and the related exocytosis were eliminated by the depletion of extracellular Ca2+. Low concentrations of bombesin (3.2 x 10(-10) M) and bethanechol (3.2 x 10(-7) M) caused sustained low-amplitude Ca2+ oscillations with correspondingly low frequencies but also caused sustained exocytosis. These data show that 1) cellular response differs between high and low concentrations of stimulus, 2) there is a close relation between [Ca2+](i) and exocytosis, 3) exocytosis follows elevation of [Ca2+](i) by 14-45 s (n = 6), and 4) there is a significant positive correlation between the peak [Ca2+](i) and the number of exocytoses.