镉对P2X4受体介导的ATP-激活电流的影响及其特征

Characteristic and effect of cadmium on ATP-activated currents mediated by P2X4 receptors

目的:研究镉对P2X4嘌呤受体介导的ATP-激活电流的影响及其特征。方法:将编码大鼠P2X4受体的cDNA在体外转录成cRNA,通过显微注射技术将该cRNA注入非洲爪蟾卵母细胞中进行表达。应用全细胞双极电压钳技术研究镉对P2X4受体介导的ATP-激活电流(IATP)的影响。结果:①在一定浓度范围内,镉可逆性地增强爪蟾卵母细胞表达的P2X4受体介导的ATP-激活电流。当镉的浓度为30μmol/L时,对ATP-激活电流的增强作用最大,超过30μmol/L时,随着镉浓度的增加,ATP-激活电流反而呈现抑制效应。②10μmol/L镉可使ATP量-效曲线左移,EC50从(17.1±1.5)μmol/L降低到(9.8±1.8)μmol/L(n=6,P<0.01),Hill系数从1.14±0.13提高到1.57±0.36;③镉对ATP-激活电流的增强作用没有电压依赖性;④当镉的孵育时间为120 s时,对ATP-激活电流增强作用最大。结论:镉增强P2X4受体介导的ATP-激活电流是可逆的,具有浓度依赖性、时间依赖性、无电压依赖性。这种作用可能是通过对P2X4受体的变构调节引起的。

Objective： To investigate the characteristic and effect of cadmium on ATP-activated currents（IATP） mediated by P2X4 purinoceptors.Methods： 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 IATP mediated by P2X4 receptor using the two-electrode whole-cell voltage clamp technique.Results： ① Within a certain concentration range,cadmium was found to reversibly magnify IATP mediated by P2X4 receptors expressed in oocytes of an xenopus.When the concentration of cadmium reached 30 μmol/L,the increase of IATP was the most significant.IATP turned to decrease when the concentration of cadmium was more than 30 μmol/L;②The concentration-response curve was shifted to left by applying cadmium at 10 μmol/L;the EC50 was reduced from（17.1±1.5） μmol/L to（9.8±1.8） μmol/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 IATP showed no dependence on membrane voltage;④The magnifying effect on IATP reached maximum when preincubating cadmium for 120 seconds.Conclusion： The increase IATP 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.