P2X currents in peritoneal macrophages of wild type and P2X4-/- mice

In this study the ATP-induced (P2X) currents in isolated peritoneal macrophages of wild type (WT) and P2X(4) knockout (P2X(4)(-/-)) mice were studied by means of whole-cell patch clamp in order to (1) survey the P2X currents of native macrophages and (2) to investigate the expression of P2X(4)-like currents in the WT versus P2X(4)(-/-) mice. Three types of currents were observed in the isolated macrophages: (1) in similar to 10% of both WT and P2X4-/- macrophages a fast activating and inactivating P2X1-like current was recorded with low concentrations (0. 1-1 mu M) of ATP; (2) 85% of wild type and 100% of P2X(4) (-/-) macrophages exhibited a non-desensitizing P2X(7)-like current activated at high concentrations of ATP (10 mM). The identity of the P2X(7) current was confirmed using the specific blocker A-740003; (3) 88.6% of the WT but none of the P2X4-/- macrophages showed a small P2X4-like current that desensitized slowly upon ATP application at intermediate concentrations (3-300 mu M). Several observations indicated that the slowly desensitizing current in WT macrophages was P2X4. The EC50 value of 5.3 mu M ATP was as expected for P2X4 and the current induced by 3-300 mu M ATP was absent in P2X4-/- mice. Upon application of 3 mu M ivermectin, a P2X(4)-selective modulator, the amplitude of this current was increased and the desensitization was inhibited in WT cells. In addition, this current was facilitated by 10 mu M Zn2+ but inhibited by Cu2+ (in contrast to P2X(2)). We conclude that the P2X4 and P2X7 currents are functionally expressed in recruited peritoneal macrophages of WT mice and that the P2X4-like current is absent in P2X(4)(-/-) mice. (C) 2007 Elsevier B.V. All rights reserved.