Calcium chelators enhance 45Ca accumulation in permeablized synaptosomes and in microsomes.
Calcium chelators enhance 45Ca accumulation in permeablized synaptosomes and in microsomes.
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钙螯合剂增强 45Ca 在透化突触体和微粒体中的积累。
DOI：
10.1152/ajpcell.1996.270.2.c628
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发表时间：
1996
期刊：
影响因子：
--
通讯作者：
Abercrombie,RF
中科院分区：
文献类型：
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作者：
Moore,JE;Abercrombie,RF
细胞内Ca ~（2+）调节的研究通常需要使用钙螯合剂来调节[Ca ~（2+）]。我们研究了这些螯合剂对微粒体和皂苷透性突触体中钙积累的影响，以评估其对表观转运特性的影响。在固定游离Ca ~（2+）为0.6 μ M时，增加乙二醇-双（β-氨乙基醚）-N，N，N '，N'-四乙酸（EGTA）和总Ca ~（2+）可增强突触体和微粒体中ATP依赖的~（45）Ca螯合。EGTA-Ca复合物不改变最大初始钙摄取率或最大稳态蓄积。相反，EGTA/Ca增加了微粒体转运蛋白对Ca 2+的表观亲和力。有机阴离子转运抑制剂丙磺舒（2.5 mM）的存在下，EGTA的存在下，45 Ca积累没有影响。用Ni 2+代替部分Ca 2+，但保持[Ca 2 +]近似恒定，降低了45 Ca摄取，表明Ni-EGTA复合物不刺激45 Ca转运。我们的研究结果表明，EGTA是不积极跨内质网膜运输，也没有二价离子结合形式的EGTA改变转运的性质。EGTA和其它具有类似结构的移动的钙螯合剂，例如，1，2-双（2-氨基苯氧基）乙烷-N，N，N '，N'-四乙酸、indo 1和fluo 3可通过向其转运位点递送更多的Ca 2+来增加钙摄取。
The study of intracellular Ca2+ regulation usually requires using calcium chelators to adjust [Ca2+]. We examined the effects of these chelators on calcium accumulation in microsomes and saponin-permeabilized synaptosomes to assess their influence on apparent transport properties. At a fixed free Ca2+ of 0.6 microM, increasing ethylene glycol-bis(beta-aminoethyl ether)-N,N,N', N'-tetraacetic acid (EGTA) and total Ca2+ enhanced ATP-dependent 45Ca sequestration in synaptosomes and microsomes. The EGTA-Ca complex did not change the maximal initial calcium uptake rate or maximal steady-state accumulation. Rather, EGTA/Ca increased the apparent affinity of the microsomal transporter for Ca2+. The presence of the organic anion transport inhibitor probenicid (2.5 mM) had no effect on 45Ca accumulation in the presence of EGTA. Replacing part of the Ca2+ with Ni2+ but maintaining [Ca2+] approximately constant reduced 45Ca uptake, suggesting that the Ni-EGTA complex did not stimulate 45Ca transport. Our results imply that EGTA is not actively transported across the endoplasmic reticulum membrane, nor does the divalent ion-bound form of EGTA change the properties of the transporter. EGTA, and other mobile calcium chelators with similar structures, e.g., 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid, indo 1, and fluo 3, may increase calcium uptake by delivering more Ca2+ to its transport site.