title: [Characteristic and effect of cadmium on ATP-activated currents mediated by P2X4 receptors].
abstract: OBJECTIVE
  To investigate the characteristic and effect of cadmium on ATP-activated currents (I(ATP)) 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 I(ATP) 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 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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Department of Physiology, Medical College, Wuhan University of Science and Technology, Wuhan 430065, China. zhangyuqin@wust.edu.cn
authors.forename: Yu-Qin
authors.initials: YQ
authors.lastname: Zhang
authors.forename: Wei-Hua
authors.initials: WH
authors.lastname: Tian
authors.forename: Fang
authors.initials: F
authors.lastname: Peng
authors.forename: Zhen
authors.initials: Z
authors.lastname: Xu
authors.forename: Yong-Li
authors.initials: YL
authors.lastname: Nie
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism*; D000818:Animals; D002104:Cadmium / Q000633:toxicity*; D008845:Microinjections; D009865:Oocytes / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology*; D051381:Rats; D058848:Receptors, Purinergic P2X4 / Q000378:metabolism*; D014982:Xenopus laevis
chemical_list: D058848:Receptors, Purinergic P2X4; D002104:Cadmium; D000255:Adenosine Triphosphate