TRINITROPHENYL-SUBSTITUTED NUCLEOTIDES ARE POTENT ANTAGONISTS SELECTIVE FOR P2X(1), P2X(3), AND HETEROMERIC P2X(2 3) RECEPTORS/

There are currently seven P2X receptor subunits (P2X(1-7)) defined by molecular cloning. The functional identification of these receptors ha s relied primarily on the potency of alpha,beta-methylene-ATP relative to that of ATP and on the kinetics of receptor desensitization. In th e present experiments we found that the 2',3'-O-(2,4,6-trinitrophenyl) -substituted analogs of ATP are selective and potent antagonists at so me but not all P2X receptors. The trinitrophenyl analogs of ATP, ADP, AMP, and GTP produced a reversible inhibition of ATP-evoked currents i n human embryonic kidney 293 cells expressing P2X(1) receptors, P2X(3) receptors, or both P2X(2) and P2X(3) (heteromeric) receptors; IC50 va lues were close to 1 nM. These compounds were at least 1000-fold less effective in blocking currents in cells expressing P2X(2), P2X(4), or P2X(7) receptors (P2X(5) and P2X(6) not tested). GTP, 2,4,6-trinitroph enol, and the 2',3'-trinitrophenyl analog of adenosine (0.1-10 mu M) h ad no effect. Thus, we have identified a structural motif that confers antagonist action at P2X receptors that contain P2X(1) or P2X(3) subu nits (the alpha,beta-methylene-ATP-sensitive subclass).