Stump R F, Oliver J M, Cragoe E J, Deanin G G
J Immunol. 1987 Aug 1;139(3):881-6.
Antigen-stimulated rat basophilic leukemia (RBL-2H3) cells release serotonin and other inflammatory mediators by a process that requires Ca2+ influx and increased cytoplasmic Ca2+ levels, and is mimicked by Ca2+ ionophores. We report here that the Ca2+ response to antigen and to ionomycin has two components, a Ca2+ spike and a Ca2+ plateau. In nominally Ca2+-free medium, both components of the Ca2+ response are inhibited and secretion does not occur. In Na+-free medium, the initial Ca2+ spike induced by antigen or ionomycin occurs, but the plateau is again absent and secretion is inhibited by 30 to 50%. Secretion is also reduced by 10(-4) M amiloride, an inhibitor of Na+ transport pathways, and by 10(-5) M concentrations of two amiloride analogs with greater activity than amiloride, respectively, against Na+ channels and Na+/Ca2+ exchange. Phorbol esters, which stimulate protein kinase C, enhance the Ca2+ plateau and secretion caused by suboptimal amounts of both antigen and ionomycin; this enhancement depends on extracellular Na+. The Na+ ionophore, monensin, mimics the Ca2+ plateau. From these data, we infer that the Ca2+ spike and plateau reflect separate responses of RBL-2H3 cells to antigen or ionomycin. We propose that the Ca2+ plateau results at least in part from the activation of a Na+-dependent Ca2+ influx pathway. One possible mechanism is that antigen binding stimulates a protein kinase C-regulated Na+ transport system. The resulting influx of Na+ may activate a Na+/Ca2+ antiporter that supports the Ca2+ plateau and mediator release.
抗原刺激的大鼠嗜碱性粒细胞白血病（RBL - 2H3）细胞通过一个需要Ca2+内流和细胞质Ca2+水平升高的过程释放5-羟色胺和其他炎症介质，并且该过程可被Ca2+离子载体模拟。我们在此报告，Ca2+对抗原和离子霉素的反应有两个成分，一个Ca2+尖峰和一个Ca2+平台期。在名义上无Ca2+的培养基中，Ca2+反应的两个成分均被抑制，且不发生分泌。在无Na+的培养基中，由抗原或离子霉素诱导的初始Ca2+尖峰出现，但平台期再次缺失，分泌被抑制30%至50%。10(-4) M的氨氯地平（一种Na+转运途径抑制剂）以及浓度为10(-5) M的两种活性比氨氯地平分别更高的氨氯地平类似物（针对Na+通道和Na+/Ca2+交换）也会使分泌减少。刺激蛋白激酶C的佛波酯可增强由次优量的抗原和离子霉素引起的Ca2+平台期和分泌；这种增强依赖于细胞外Na+。Na+离子载体莫能菌素模拟Ca2+平台期。根据这些数据，我们推断Ca2+尖峰和平台期反映了RBL - 2H3细胞对抗原或离子霉素的不同反应。我们提出Ca2+平台期至少部分是由一种依赖Na+的Ca2+内流途径的激活导致的。一种可能的机制是抗原结合刺激了一种蛋白激酶C调节的Na+转运系统。由此产生的Na+内流可能激活一个Na+/Ca2+反向转运体，该转运体支持Ca2+平台期和介质释放。
