Loessberg P A, Zhao H, Muallem S
Department of Physiology, University of Texas Southwestern Medical Center, Dallas 75235.
J Biol Chem. 1991 Jan 25;266(3):1363-6.
Oscillation in [Ca2+]i induced by agonists has been described in many cell types and is thought to reflect Ca2+ release from and uptake into internal stores. We measured [Ca2+]i and Mn2+ entry in single cells of the pancreatic acinar cell line AR42J loaded with Fura 2 to examine the behavior of Ca2+ influx across the plasma membrane (Ca2+ entry) during agonist-evoked [Ca2+]i oscillation. Addition of extracellular Ca2+ (Ca2+out) to agonist-stimulated cells bathed in Ca2(+)-free medium resulted in a marked [Ca2+]i increase blocked by La3+. The use of Mn2+ as a congener of Ca2+ to follow unidirectional Ca2+ movement reveals an oscillatory activation of Ca2+ entry by Ca2(+)-mobilizing agonists. The frequency at which Ca2+ entry oscillated matched the frequency of Ca2+ release from intracellular stores. Ca2+ entry is activated after completion of Ca2+ release and is inactivated within the time span of each [Ca2+]i spike. These studies reveal a new aspect of [Ca2+]i oscillation in agonist-stimulated cells, that is the oscillatory activation of [Ca2+]i entry during [Ca2+]i oscillation.
激动剂诱导的[Ca2+]i振荡已在多种细胞类型中被描述，并且被认为反映了Ca2+从内部储存库的释放和摄取。我们测量了加载有Fura 2的胰腺腺泡细胞系AR42J单细胞中的[Ca2+]i和Mn2+内流，以研究在激动剂诱发的[Ca2+]i振荡期间跨质膜的Ca2+内流（Ca2+进入）行为。向浸泡在无Ca2+培养基中的激动剂刺激细胞添加细胞外Ca2+（Ca2+out）导致[Ca2+]i显著增加，该增加被La3+阻断。使用Mn2+作为Ca2+的同类物来追踪单向Ca2+运动，揭示了Ca2+动员激动剂对Ca2+进入的振荡性激活。Ca2+进入振荡的频率与细胞内储存库中Ca2+释放的频率相匹配。Ca2+进入在Ca2+释放完成后被激活，并在每个[Ca2+]i峰值的时间范围内失活。这些研究揭示了激动剂刺激细胞中[Ca2+]i振荡的一个新方面，即在[Ca2+]i振荡期间[Ca2+]i进入的振荡性激活。
