High cytosolic pH inhibits Ca uptake by Myxicola axon mitochondria.
High cytosolic pH inhibits Ca uptake by Myxicola axon mitochondria.
复制标题
高胞质 pH 值抑制 Myxicola 轴突线粒体对 Ca 的吸收。
DOI：
10.1152/ajpcell.1987.252.1.c68
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发表时间：
1987
期刊：
影响因子：
--
通讯作者：
K. Gammeltoft
中科院分区：
文献类型：
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作者：
R. Abercrombie;K. Gammeltoft
从海洋环节动物巨轴突抽取含有线粒体的细胞质微升样品，并将其吸入聚乙烯管中。这些细胞质样品中的小分子成分由透析毛细管控制，具有6000分子量切断。用离子敏感微电极监测样品的钙离子活性（pCa）的负对数（6.72 +/- 0.03,n = 40），在某些情况下，pH （7.51 +/- 0.01, n = 7）。在pH 7.5下加入5毫米琥珀酸盐或5毫米ATP，导致细胞质中的Ca活性从实验升高的约10微米降至1微米以下。这种减少可以被钌红抑制，提示线粒体机制。加入琥珀酸盐或ATP后，当细胞质pH升高到8.3左右时，钙的摄取可逆地减慢。在线粒体吸收钙后加入钌红，线粒体外细胞质中的钙活性逐渐增加，表明钙从储存部位持续释放。在钌红存在的情况下，将细胞质pH值增加到约8.5并不比单独使用钌红时增加持续释放。不依赖能量的非线粒体钙缓冲液中钙的明显冲洗仅受pH值（7.5-8.5）的轻微影响。结果表明，细胞内pH升高至8.3会减缓线粒体对钙的吸收。因此，细胞质pH值可能具有调节线粒体钙代谢和/或线粒体外钙活性的功能。
Microliter samples of cytoplasm containing mitochondria were aspirated from giant axons of the marine annelid Myxicola infundibulum into polyethylene tubes. The small molecular constituents within these cytoplasmic samples were controlled by a dialysis capillary with a 6,000 molecular weight cut off. The negative log of the calcium ion activity (pCa) (6.72 +/- 0.03, n = 40) and, in some cases, the pH (7.51 +/- 0.01, n = 7) of the samples were monitored with ion-sensitive microelectrodes. Adding 5 mM succinate or 5 mM ATP at pH 7.5 caused the Ca activity in the cytoplasm to drop from an experimentally elevated value of approximately 10 microM to below 1 microM. This decrease could be inhibited with ruthenium red, suggesting a mitochondrial mechanism. Ca uptake, following the addition of either succinate or ATP, was reversibly slowed when the cytoplasmic pH was elevated to approximately 8.3. When ruthenium red was added after mitochondria had taken up Ca, the Ca activity in the extramitochondrial cytoplasm gradually increased suggesting ongoing release of Ca from storage sites. Increasing the cytoplasmic pH to approximately 8.5 in the presence of ruthenium red did not increase the ongoing release over that found with ruthenium red alone. The apparent washout of Ca from the energy-independent, nonmitochondrial Ca buffers was only slightly affected by pH (pH 7.5-8.5). It is concluded that elevating intracellular pH to 8.3 slows the Ca uptake by mitochondria. Thus cytoplasmic pH may have a function in regulating mitochondrial Ca metabolism and/or extramitochondrial calcium activity.