EFFECTS OF MECH, THAPSIGARGIN, AND LA-3+ ON PLASMALEMMAL AND INTRACELLULAR CA-2+ TRANSPORT IN LACRIMAL ACINAR-CELLS
EFFECTS OF MECH, THAPSIGARGIN, AND LA-3+ ON PLASMALEMMAL AND INTRACELLULAR CA-2+ TRANSPORT IN LACRIMAL ACINAR-CELLS
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DOI：
10.1152/ajpcell.1990.258.6.c1006
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发表时间：
1990-06-01
影响因子：
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通讯作者：
PUTNEY, JW
中科院分区：
文献类型：
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作者：
KWAN, CY;TAKEMURA, H;PUTNEY, JW
研究了muscarinic受体激动剂methacholine （MeCh）和微粒体Ca2+泵抑制剂thapsigargin在泪腺泡细胞中的Ca2（+）动员作用。正如之前所显示的腮腺细胞(J. Biol。化学，264:12266-12271,1989)，thapsigargin激活内部Ca2+释放和Ca2+从细胞外空间进入，而不增加细胞肌醇磷酸。无机Ca2+拮抗剂La3+抑制MeCh-或thapsigarin激活的Ca2+进入。然而，当在MeCh或thapsigargin之前加入La3+时，La3+抑制了Ca2+在质膜上的挤压。这一现象被利用的方案设计，以研究途径填补激动剂敏感的Ca2+储存在泪细胞。结果表明，与之前认为需要外部Ca2+来补充激动剂调节的Ca2+储存的建议相反，抑制Ca2+挤压允许MeCh释放的Ca2+再循环回到MeCh-和thapsigarin敏感的池中。因此，尽管在生理条件下，细胞外Ca2+是细胞内Ca2+储存的主要来源，但这种Ca2+进入池的途径不一定是直接的。这些结果与最近修订的细胞内Ca2+储存通过Ca2+内流再填充的电容模型一致，随后Ca2+耗尽，根据细胞内Ca2+储存的再填充是通过细胞质途径发生的，而不是细胞内Ca2+储存和细胞外空间之间的直接通道。
The Ca2(+)-mobilizing actions of the muscarinic receptor agonist, methacholine (MeCh), and the microsomal Ca2+ pump inhibitor, thapsigargin, were investigated in lacrimal acinar cells. As previously shown for parotid cells (J. Biol. Chem. 264: 12266-12271, 1989), thapsigargin activates both internal Ca2+ release and Ca2+ entry from the extracellular space without increasing cellular inositol phosphates. The inorganic Ca2+ antagonist La3+ inhibited MeCh- or thapsigargin-activated Ca2+ entry. However, when added before MeCh or thapsigargin, La3+ inhibited the extrusion of Ca2+ at the plasma membrane. This phenomenon was exploited in protocols designed to investigate the pathways for filling agonist-sensitive Ca2+ stores in lacrimal cells. The results show that, in contrast to previous suggestions that external Ca2+ is required to replenish agonist-regulated Ca2+ stores, the inhibition of Ca2+ extrusion permits recycling of Ca2+ released by MeCh back into an MeCh- and thapsigargin-sensitive pool. Thus, although extracellular Ca2+ is the major source for refilling the intracellular Ca2+ stores under physiological conditions, the pathway by which this Ca2+ enters the pool need not be a direct one. These results are consistent with the recently revised capacitative model for the refilling of intracellular Ca2+ stores through Ca2+ influx subsequent to Ca2+ depletion, according to which refilling of intracellular Ca2+ stores occurs via a cytoplasmic route rather than a direct channel between intracellular Ca2+ stores and the extracellular space.