Plasman P O, Lebrun P, Herchuelz A
Laboratory of Pharmacology, Brussels University, School of Medicine, Belgium.
Am J Physiol. 1990 Dec;259(6 Pt 1):E844-50. doi: 10.1152/ajpendo.1990.259.6.E844.
Na(+)-Ca2+ exchange may play a role in Ca2+ extrusion from the pancreatic B-cell. The characteristics of the process working in its reverse mode were examined in normal rat pancreatic islet cells. Isosmotical replacement of extracellular Na+ by sucrose induced a concentration-dependent increase in 45Ca uptake, displaying a pharmacological sensitivity compatible with an uptake mediated by Na(+)-Ca2+ exchange. Glucose, up to 2.8 mM, stimulated reverse Na(+)-Ca2+ exchange. Likewise, membrane depolarization activated the process but only under raised intracellular Na+ activity. In conclusion, the B-cell Na(+)-Ca2+ exchange displays properties similar to those observed in other cells: reversibility and sensitivity to membrane potential. When working in its reverse mode the exchanger displays a quite large capacity. The role played by the exchanger in the process of insulin release warrants further investigation.
钠钙交换可能在胰腺β细胞的钙排出过程中发挥作用。我们在正常大鼠胰岛细胞中研究了该过程逆向模式的工作特性。用蔗糖等渗替代细胞外钠会导致45钙摄取呈浓度依赖性增加，显示出与钠钙交换介导的摄取相一致的药理学敏感性。高达2.8 mM的葡萄糖刺激逆向钠钙交换。同样，膜去极化激活该过程，但仅在细胞内钠活性升高时。总之，β细胞钠钙交换表现出与其他细胞中观察到的特性相似：可逆性和对膜电位的敏感性。当以逆向模式工作时，交换器显示出相当大的容量。交换器在胰岛素释放过程中所起的作用值得进一步研究。
