Janis R A, Crankshaw D J, Daniel E E
Am J Physiol. 1977 Jan;232(1):C50-8. doi: 10.1152/ajpcell.1977.232.1.C50.
Four fractions enriched, respectively, in plasma membrane (PM), smooth endoplasmic reticulum (SER), rough endoplasmic reticulum (RER), and mitochondria were isolated from estrogen-dominated rat myometrium. Ca2+ uptake by these fractions was studied in order to estimate the relative potential of the corresponding organelles for controlling intracellular Ca2+ activity. Ca2+ uptake properties of the PM, SER, and RER fractions were similar except that potentiation by oxalate was in the order RER greater than or equal SER greater than PM. However, studies with the ionophores X-537A and A23187 suggested that Ca2+ was transported into the lumen of membrane vesicles of all these fractions. Unlike that of skeletal muscle sarcoplasmic reticulum, Ca2+ uptake by the myometrial fractions was not supported by high-energy compounds other than ATP. Mitochondria took up much less Ca2+ at low, and much more Ca2+ at high, free Ca2+ concentrations than did the other fractions. The amount of Ca2+ taken up in 30 s from a 1 muM free Ca2+ solution in the presence of ATP was similar for all fractions. These results suggested that mitochondria may act as an important Ca2+ control system in rat myometrium when the intracellular Ca2+ concentration is near 1 muM or higher, whereas the PM, SER, and RER may be of major importance at Ca2+ levels of 0.3 muM or lower.
从雌激素占主导的大鼠子宫肌层中分离出分别富含质膜（PM）、滑面内质网（SER）、粗面内质网（RER）和线粒体的四个组分。研究了这些组分对钙离子的摄取情况，以评估相应细胞器控制细胞内钙离子活性的相对能力。PM、SER和RER组分的钙离子摄取特性相似，只是草酸盐的增强作用顺序为RER≥SER＞PM。然而，用离子载体X-537A和A23187进行的研究表明，钙离子被转运到所有这些组分的膜泡腔中。与骨骼肌肌浆网不同，子宫肌层组分对钙离子的摄取不受ATP以外的高能化合物支持。在游离钙离子浓度较低时，线粒体摄取的钙离子比其他组分少得多，而在游离钙离子浓度较高时，线粒体摄取的钙离子则比其他组分多得多。在ATP存在的情况下，所有组分在30秒内从1μM游离钙离子溶液中摄取的钙离子量相似。这些结果表明，当细胞内钙离子浓度接近1μM或更高时，线粒体可能是大鼠子宫肌层中重要的钙离子控制系统，而在钙离子水平为0.3μM或更低时，PM、SER和RER可能起主要作用。
