Na^+／Ca^2+交换介导的Nd^3+跨淋巴细胞膜的行为研究

利用Fura-2荧光浓度指示剂法对Na^+／Ca^2+交换介导的Nd^3+跨入外赂血淋巴 细胞膜行为进行了一系列研究。结果表明：当细胞形成向外的Na^+梯度时Nd^3+能 跨膜进入细胞,电压依赖性L-型Ca^2+通道对Nd^3+进入无贡献,提出了Na^+／ Ca^2+交换系统是Nd^3+进入细胞的主要途径;在安全浓度范围内进入胞内的游 Nd^3+浓度成正比,计算表明进入胞内的最大游离Nd^3+浓度为（3.67±0.32）× 10^-14mol·L^-1;当胞外pH值降低时进入胞内的游离Nd^3+浓度减小,胞内游离 Ca^2+浓度减小时进入的游离Nd^3+浓度略微增大,胞外Nd^3+和Ca^2+竞争Na^+／ Ca^2+交换位点;结果进一步推测进入胞内的Nd^3+可被质膜钙泵泵出胞外,初步实 验表明进入胞浆中的Nd^3+会在内质网中进一步累积,而在线粒体中不累积。

Nd~3 + Influx Mediated by the Na~+/Ca~2 + Exchange in Human Lymphocytes

A series of experiments on Nd~3 + influx mediated by the Na~+ /Ca~2 + exchange in human lymphocytes were processed by fura-2 method. The results show that when the cellular Na~+ gradient is reversed, Nd~3 can enter the lymphocytes and voltage dependent calcium channels are not responsible for Nd ~+ influx. It suggests that the Na~+/ Ca ~+ exchange provides a major route for Nd ~+ entry in human lymphocytes. Intracellular free Nd concentrations (Nd~3]i) are directly proportional to extracellular free Nd~3+ concentrations (Nd~3+ ]-0) and the maximum Nd~3+ ]j is (3.67 ±0.32) x 10" mol*L~-1 . Nd ~+ ]-i decreases with decreasing extracellular pH but increases with decreasing intracellular Ca~2+ ];. The Ca~+ influx and Nd~3+ influx mediated by the Na~+/Ca~2+ exchange might be mutually competitive. Furthermore, the results also suggest that cytosolic Nd ~+ is transported by the ATP-dependent Ca pump and intracellular Nd ~+ appears to be taken up by endoplasmic reticulum and not be significantly accumulated by mitochondria.