Coutinho-Silva R, Alves L A, de Carvalho A C, Savino W, Persechini P M
Instituto de Biofisica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Brazil.
Biochim Biophys Acta. 1996 Apr 26;1280(2):217-22. doi: 10.1016/0005-2736(95)00293-6.
The thymic microenvironment is under intrinsic and extrinsic control circuits by several elements including hormones, neuropeptides, lymphokines, innervation and cell contact. P2 purinergic receptors have been described in a number of cells including macrophages, thymocytes, and other cells of the immune-inflammatory system. Here, we use the whole-cell patch-clamp technique and dye permeabilization assays to investigate the presence of ionic channels and purinergic receptors in one microenvironmental thymic component, namely the phagocytic cell of the thymic reticulum. At holding potentials ranging from -30 to -60 mV, applications of extracellular ATP in the vicinity of the cell membrane induce a transient and fast-activating inward current followed in most cells by an outward current. The whole event lasts 5-20 s. The inward current has a reversal potential close to 0 mV and the outward current can be ascribed to a Ca2+ -dependent K+ conductance. Both currents are inhibited by Mg2+, suggesting that the phenomenon is mediated by ATP4-. ATP-gamma-S can also induce both inward and outward currents. Exposure of phagocytic cells of the thymic reticulum to 5 mM ATP for 10 min induced permeabilization to lucifer yellow but not to the larger dyes trypan blue and rhodamine-dextran, suggesting a molecular weight cut-off smaller than 900. These observations lead us to conclude that phagocytic cells of the thymic reticulum express P2Z purinergic receptors that can mobilize Ca2+, induce the opening of ionic channels and permeabilize the cell membrane.
胸腺微环境受多种因素的内在和外在控制回路调节，这些因素包括激素、神经肽、淋巴因子、神经支配和细胞接触。P2嘌呤能受体已在包括巨噬细胞、胸腺细胞和免疫炎症系统的其他细胞在内的多种细胞中被描述。在这里，我们使用全细胞膜片钳技术和染料通透试验来研究胸腺微环境成分之一，即胸腺网状组织的吞噬细胞中离子通道和嘌呤能受体的存在情况。在-30至-60 mV的钳制电位下，在细胞膜附近施加细胞外ATP会诱导一个短暂且快速激活的内向电流，随后在大多数细胞中会出现外向电流。整个过程持续5-20秒。内向电流的反转电位接近0 mV，外向电流可归因于Ca2+依赖性K+电导。两种电流均受Mg2+抑制，这表明该现象是由ATP4-介导的。ATP-γ-S也可诱导内向和外向电流。将胸腺网状组织的吞噬细胞暴露于5 mM ATP 中10分钟会诱导其对荧光素黄通透，但对较大的染料台盼蓝和罗丹明葡聚糖不通透，这表明分子量截断值小于900。这些观察结果使我们得出结论，胸腺网状组织的吞噬细胞表达P2Z嘌呤能受体，该受体可动员Ca2+、诱导离子通道开放并使细胞膜通透。
