Somlyo A P, Wasserman A J, Kitazawa T, Bond M, Shuman H, Somlyo A V
Experientia. 1985 Aug 15;41(8):981-8. doi: 10.1007/BF01952118.
Electron probe microanalysis (EPMA) has been used to study the subcellular distribution of Ca, Na, K, Cl, and Mg in smooth muscle. The EPMA results indicate that the sarcoplasmic reticulum (SR) is the major intracellular source and sink of activator Ca: norepinephrine decreases the Ca content of the junctional SR in portal vein smooth muscle. Mitochondria do not play a significant role in regulating cytoplasmic free Ca2+, but mitochondrial Ca content can be altered to a degree compatible with suggestions that fluctuations in matrix Ca contribute to the control of mitochondrial metabolism. The rise in total cytoplasmic Ca during a maintained, maximal contraction is very much greater than the rise in free Ca2+, and is probably in excess of the known binding sites available on calmodulin and myosin. Cell Ca is not increased in normal cells that are Na-loaded. The non-Donnan distribution of Cl is not due to compartmentalization, but reflects high cytoplasmic Cl. Na-loading of smooth muscle in K-free solutions is temperature dependent, and may exhibit cellular heterogeneity undetected by conventional techniques. The total cell Mg is equivalent to approximately 12 mM, and less than 50% of it can be accounted for by binding to ATP and to actin. Mitochondrial monovalent cations in smooth muscle are relatively rapidly exchangeable.
电子探针微量分析（EPMA）已被用于研究平滑肌中钙、钠、钾、氯和镁的亚细胞分布。EPMA结果表明，肌浆网（SR）是激活钙的主要细胞内来源和储存库：去甲肾上腺素降低门静脉平滑肌连接肌浆网的钙含量。线粒体在调节细胞质游离钙方面不起重要作用，但线粒体钙含量可在一定程度上改变，这与基质钙波动有助于控制线粒体代谢的观点相符。在持续的最大收缩过程中，细胞质总钙的升高远大于游离钙的升高，可能超过了钙调蛋白和肌球蛋白上已知的结合位点。在钠负荷的正常细胞中，细胞钙不会增加。氯的非唐南分布不是由于分隔，而是反映了高细胞质氯。在无钾溶液中平滑肌的钠负荷是温度依赖性的，可能表现出传统技术未检测到的细胞异质性。细胞总镁约相当于12 mM，其中不到50%可通过与ATP和肌动蛋白结合来解释。平滑肌中的线粒体单价阳离子相对快速可交换。
