Abstract

To further elucidate the modulator role of trace metals such as zinc and copper on the activity of nucleotide purinoceptors, the action of these metals was assessed during prolonged ATP applications to rat P2X4 purinoceptors expressed in Xenopus laevis oocytes. Application of ATP for 3 min resulted in a biphasic effect; a fast transient peak was followed by a slower stable current component with similar pharmacological and biophysical characteristics. The application of 1-300 ?M Cu2+ inhibited both current components to a comparable extent; likewise, Zn2+ facilitated to a similar degree the transient and the slower stable current components. Carnosine (Car), cysteine (Cys), histidine (His), and the metal chelator, penicillamine, prevented the inhibitory action of Cu2+; the Zn2+ facilitation was not prevented by neither Car nor His but by either bathophenantroline or Cys, revealing metal selectivity. While the noncompetitive Cu2+ inhibition appears to decrease channel conductance, Zn2+ likely increases ATP affinity independently of the activation state of the purinoceptor. These results strongly support the notion that trace metals modulate the activity of the P2X4 purinoceptor and could become relevant during continual activity of a P2X4 purinoceptor-containing synapse. © 2003 Elsevier Science B.V. All rights reserved.