Table 3

Functional properties of recombinant heteromeric P2X receptors

Heteromeric Receptor Type
Agonists EC50 (μM)
Antagonists IC50 (μM)
 SuraminBlock 30–100 μMBlock 10 μM1.6 μM6
 PPADSBlock 3–300 μMBlock 10 μM0.6 μM
 TNP-ATP0.007 μM0.4 μM
 Brilliant Blue G>10 μM>10 μM
Ion effects
 Zn2+ Potentiation EC50 6 μM
 H+ Potentiation at pH 6.3, block at pH 8.3Block at pH greater or less than pH 7.3Potentiation p Ka 7 Block pH 6.5–4
 Ca2+ Block IC50 15 mMNo effect on peak, but plateau is potentiated
  • The P2X4/6 heteromer is blocked to a slightly greater degree by suramin and PPADS than homomeric P2X4 channels (Le et al., 1998a), but IC50 or affinity estimates are unknown. Data in the table are from the following references: Lewis et al., 1995;Radford et al., 1997; Le et al., 1998a, 1999; Thomas et al., 1998;Torres et al., 1998b, 1999; Virginio et al., 1998a,b; Haines et al., 1999; King et al., 2000; Surprenant et al., 2000.