Zhang Yu-Qin, Tian Wei-Hua, Peng Fang, Xu Zhen, Nie Yong-Li
Department of Physiology, Medical College, Wuhan University of Science and Technology, Wuhan 430065, China.
Zhongguo Ying Yong Sheng Li Xue Za Zhi. 2012 Sep;28(5):430-4.
To investigate the characteristic and effect of cadmium on ATP-activated currents (I(ATP)) mediated by P2X4 purinoceptors.
Transcribe cDNA coding for the rat P2X4 receptor to cRNA in vitro. Inject the cRNA to oocytes of an xenopus laevis using the microinjection technique. Reveal the effect of cadmium on I(ATP) mediated by P2X4 receptor using the two-electrode whole-cell voltage clamp technique.
(1) Within a certain concentration range, cadmium was found to reversibly magnify I(ATP) mediated by P2X4 receptors expressed in oocytes of an xenopus. When the concentration of cadmium reached 30 micromol/L, the increase of I(ATP) was the most significant. I(ATP) turned to decrease when the concentration of cadmium was more than 30 micromol/L; (2) The concentration-response curve was shifted to left by applying cadmium at 10 micromol/L; the EC50 was reduced from (17.1 +/- 1.5) micromol/L to (9.8 +/- 1.8) micromol/L (n = 6, P < 0.01) and the Hill coefficient was increased from 1.14 +/- 0.13 to 1.57 +/- 0.36; (3) The effect of cadmium on I(ATP) showed no dependence on membrane voltage; (4) The magnifying effect on I(ATP) reached maximum when preincubating cadmium for 120 seconds.
The increase I(ATP) by cadmium is reversible, concentration-dependent, time-dependent, and voltage-independent. One reason of this augment effect could be the allosteric modulation on P2X4 receptors.
研究镉对P2X4嘌呤受体介导的ATP激活电流（I(ATP)）的特性及影响。
在体外将编码大鼠P2X4受体的cDNA转录为cRNA。采用显微注射技术将cRNA注入非洲爪蟾卵母细胞。运用双电极全细胞膜片钳技术揭示镉对P2X4受体介导的I(ATP)的影响。
（1）在一定浓度范围内，发现镉可使非洲爪蟾卵母细胞中表达的P2X4受体介导的I(ATP)可逆性增大。当镉浓度达到30 μmol/L时，I(ATP)的增加最为显著。当镉浓度超过30 μmol/L时，I(ATP)开始下降；（2）施加10 μmol/L镉时，浓度-反应曲线左移；半数有效浓度（EC50）从（17.1±1.5）μmol/L降至（9.8±1.8）μmol/L（n = 6，P < 0.01），希尔系数从1.14±0.13增至1.57±0.36；（3）镉对I(ATP)的影响不依赖于膜电压；（4）镉预孵育120秒时，对I(ATP)的放大作用达到最大。
镉使I(ATP)增加具有可逆性、浓度依赖性、时间依赖性和电压依赖性。这种增强作用的一个原因可能是对P2X4受体的变构调节。
