CHARACTERIZATION OF SUSTAINED [CA-2+]I INCREASE IN PANCREATIC ACINAR-CELLS AND ITS RELATION TO AMYLASE SECRETION
CHARACTERIZATION OF SUSTAINED [CA-2+]I INCREASE IN PANCREATIC ACINAR-CELLS AND ITS RELATION TO AMYLASE SECRETION
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DOI：
10.1152/ajpgi.1990.259.5.g792
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发表时间：
1990-11-01
影响因子：
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通讯作者：
WILLIAMS, JA
中科院分区：
文献类型：
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作者：
TSUNODA, Y;STUENKEL, EL;WILLIAMS, JA
通过 fura-2 的显微分光荧光分析，在用氨甲酰胆碱 (10-5 M) 最大刺激大鼠胰腺腺泡期间，研究了单个腺泡细胞中胞质游离 Ca2+ 浓度 ([Ca2+]i) 的持续增加。细胞内储存的 [Ca2+]i 初始大幅增加后，只要施加刺激，[Ca2+]i 就会保持显着升高。该平台的幅度取决于中位 Ca2+ 浓度 ([Ca2+]o)，在含有 1 mM [Ca2+]o 的培养基中高于预刺激 45-50 nM，在 10 mM [Ca2+]o 时增加至 90 nM。该 Ca2+ 平台被 2.5 mM Ni2+ 和 0.25 mM La3+ 完全阻断，但不受升高的 K+ 或 Ca2+ 通道阻断剂 D 600 的影响。细胞刺激后，Mn2+ 能够进入细胞质，如细胞内淬灭 fura-2 所示，表明腺泡细胞具有 Mn2+ 可渗透的 Ca2+ 通道。在灌流条件下，消除[Ca2+]o或向培养基中添加Ni2+和Mn2+以可逆的方式降低了持续淀粉酶分泌的水平。通过增加 [Ca2+]o 将 [Ca2+]i 增加到正常水平以上对淀粉酶分泌没有影响。 Ca2+持续进入的过程对pH值敏感；在细胞刺激过程中，将细胞外 pH (pHo) 降低至 6.5-6.8，导致持续 [Ca2+]i 平台水平降低和持续淀粉酶分泌减少。相比之下，将 pHo 增加到 8.0 以 Ni2+ 敏感的方式增强了持续 [Ca2+]i 的水平，但没有增加淀粉酶的释放。细胞质 pH 值的变化对持续 [Ca2+]i 平台的影响很小。结果证明了受体介导的 Ca2+ 进入机制，导致 [Ca2+]i 小幅增加，这对于维持淀粉酶的持续释放至关重要。
The sustained increase in cytosolic free Ca2+ concentration ([Ca2+]i) during maximal stimulation of rat pancreatic acini with carbamylcholine (10-5 M) was investigated in individual acinar cells by microspectrofluorometric analysis of fura-2. After the large initial [Ca2+]i increase from intracellular stores, [Ca2+]i remained significantly elevated a long as the stimulus was applied. The amplitude of this plateau was dependent on the median Ca2+ concentration ([Ca2+]o) being 45-50 nM above prestimulation in medium with 1 mM [Ca2+]o increasing to 90 nM at 10 mM [Ca2+]o. This Ca2+ plateau was completely blocked by 2.5 mM Ni2+ and 0.25 mM La3+ but was unaffected by elevated K+ or the Ca2+ channel blocker D 600. Mn2+ was able to enter the cytosol after the cell stimulation as indicated by intracellular quenching the fura-2, indicating that acinar cells possess a Mn2+-permeable Ca2+ channel. Elimination of [Ca2+]o or addition of Ni2+ and Mn2+ to the medium reduced the level of sustained amylase secretion in a reversible manner under superfusion conditions. Increasing [Ca2+]i above the normal level by increasing [Ca2+]o had no effect on amylase secretion. The process of sustained Ca2+ entry was pH sensitive; decreasing extracellular pH (pHo) to 6.5-6.8 during the cell stimulation resulted in a reduction of the sustained [Ca2+]i plateau level and a decreased in sustained amylase secretion. By contrast, increasing pHo to 8.0 enhanced the level of the sustained [Ca2+]i in a Ni2+-sensitive manner but did not increase amylase release. Changes in cytosolic pH had only minimal effects of the sustained [Ca2+]i plateau. The results demonstrate a receptor-mediated Ca2+ entry mechanism, which results in a small increase in [Ca2+]i important in the maintenance of sustained amylase release.