Prentki M, Janjic D, Wollheim C B
J Biol Chem. 1984 Nov 25;259(22):14054-8.
Experiments aimed at the partial reconstitution of the intracellular transport systems regulating the cytosolic free Ca2+ homeostasis are reported. Rat insulinoma subcellular fractions enriched in mitochondria, endoplasmic reticulum (microsomes), and secretory granules were studied. The ambient free Ca2+ concentration maintained by the separate or combined organelles was determined with a Ca2+-selective minielectrode. The data demonstrate that ambient [Ca2+] is established by the microsomes, not by the mitochondria or the secretory granules, in the range of resting cytosolic Ca2+ concentrations (0.1-0.2 microM Ca2+). Furthermore, the microsomes are able to deplete largely the mitochondria of their exchangeable calcium. Nonetheless, both mitochondria and microsomes, but not secretory granules, function as a coordinated unit to restore the previous ambient [Ca2+] following its perturbation. Thus, mitochondria play a major role in bringing down rapidly ambient [Ca2+] to the submicromolar range, whereas the endoplasmic reticulum acts as a relay in the transport mechanisms which lower [Ca2+] to the resting level.
本文报道了旨在部分重建调节胞质游离钙离子稳态的细胞内运输系统的实验。研究了富含线粒体、内质网（微粒体）和分泌颗粒的大鼠胰岛素瘤亚细胞组分。用钙离子选择性微电极测定了由单独或组合的细胞器维持的细胞外游离钙离子浓度。数据表明，在静息胞质钙离子浓度（0.1 - 0.2微摩尔/升钙离子）范围内，细胞外[钙离子]由微粒体建立，而非线粒体或分泌颗粒。此外，微粒体能够大量耗尽线粒体中可交换的钙。尽管如此，线粒体和微粒体（而非分泌颗粒）在细胞外[钙离子]受到扰动后，作为一个协调单位发挥作用以恢复先前的细胞外[钙离子]。因此，线粒体在迅速将细胞外[钙离子]降至亚微摩尔范围内起主要作用，而内质网在将[钙离子]降至静息水平的运输机制中起中继作用。
