Actions of antagonists, pH and metal ions on <i>Lym</i>P2X currents.

<p>The effects of the P2 receptor antagonists suramin and PPADS, pH and zinc and copper on ATP evoked <i>Lym</i>P2X currents were determined in <i>Xenopus</i> oocytes. (A) Inhibition curves for mean responses to 10 µM ATP in the presence of suramin (open circles) and PPADS (closed circles) (n = 5−9 oocytes). Mean peak currents (± s.e.m) are normalized to responses evoked by 10 µM ATP in the absence of antagonist. (B) Representative current traces for data plotted in A) demonstrating the inhibitory effects of different concentrations of PPADS or suramin on the current response evoked by 10 µM ATP (black bar). Antagonists were bath perfused and also present in the ATP application at the appropriate concentration. (C) Concentration response curves for ATP in recording solutions of different pH. Alkaline pH 8.5 had no effect on ATP efficacy or potency whereas acidic pH 6.5 reduced current amplitudes (n = 6). Mean peak currents (± s.e.m) are normalized to responses evoked by 10 µM ATP at pH 7.5. (D) Biphasic effects of Zn²⁺ and Cu²⁺ on ATP (10 µM) evoked <i>Lym</i>P2X currents. Mean peak currents (± s.e.m) are normalized to responses evoked by 10 µM ATP in the absence of metal ion. Both Zn²⁺ and Cu²⁺ potentiated ATP evoked current amplitude when present at 100 µM (p<0.05 (*) for Zn²⁺ and p<0.01 (**) for Cu²⁺) but inhibited ATP evoked currents when present at a concentration of 1 mM (p<0.01) (n = 5−8).