Hurley T W
Department of Child Health, University of Missouri School of Medicine, Columbia 65212.
Am J Physiol. 1988 May;254(5 Pt 1):C621-7. doi: 10.1152/ajpcell.1988.254.5.C621.
Energy-dependent subcellular Ca2+ sequestration was studied in the presence of ruthenium red using rat pancreatic acini, which had been permeabilized by exposure to medium nominally free of Ca2+. The initial rate of Ca2+ uptake (approximately 2,800 pmol.min-1.mg acinar protein-1) quickly slowed, and a mean steady-state Ca2+ content of approximately 3,000 pmol/mg was reached after 5-10 min of incubation at 37 degrees C. Ca2+ uptake was stimulated by submicromolar Ca2+ concentrations (K0.5 = 156 nM); required Mg2+-ATP (K0.5 = 0.78 mM) was greatest at a pH of 7.0 and was abolished by the Ca2+ ionophore A23187. Other nucleotide phosphates as well as p-nitrophenylphosphate were relatively poor substrates, supporting Ca2+ uptake at initial rates that were 6-14% of those measured in the presence of ATP. These results show that pancreatic acini permeabilized without detergents possess a nonmitochondrial Ca2+ transporting system not located in the plasma membrane but with the properties expected of a major regulator of acinar cytosolic Ca2+ concentration.
在钌红存在的情况下，使用大鼠胰腺腺泡研究了能量依赖的亚细胞Ca2+隔离，这些腺泡通过暴露于名义上不含Ca2+的培养基中而被透化。Ca2+摄取的初始速率（约2800 pmol·min-1·mg腺泡蛋白-1）迅速减慢，在37℃孵育5-10分钟后达到约3000 pmol/mg的平均稳态Ca2+含量。亚微摩尔浓度的Ca2+刺激Ca2+摄取（K0.5 = 156 nM）；所需的Mg2+-ATP（K0.5 = 0.78 mM）在pH 7.0时最大，并被Ca2+离子载体A23187消除。其他核苷酸磷酸酯以及对硝基苯磷酸酯是相对较差的底物，以初始速率支持Ca2+摄取，该初始速率是在ATP存在下测得的初始速率的6-14%。这些结果表明，未经去污剂透化的胰腺腺泡具有一种非线粒体Ca2+转运系统，该系统不位于质膜中，但具有腺泡细胞质Ca2+浓度主要调节因子所预期的特性。
