Fig. 1.

Bile acids inhibit rat P2X2 at micromolar concentrations. a Representative current traces of Xenopus laevis oocytes expressing rat P2X2; P2X2 was activated by ATP (10 μM, black bar). Blue bars indicate the addition of 20 μM of different bile acids or control (solution exchange only). b Mean current amplitudes in the presence of the indicated substance relative to the ATP-activated current prior to substance application. Error bars represent standard error of the mean (S.E.M.), **p < 0.005, ***p < 0.001; n = 7–11. c Structure of TLCA with its conjugated taurine group indicated in gray. Hydroxy groups at the three carbon atoms highlighted by their IUPAC number discriminate the tested bile acids. The hydroxyl groups of each bile acid with their steric orientation are summarized in the table. TLCA, taurolithocholic acid; TCDCA, taurochenodeoxycholic acid; TUDCA, tauroursodeoxycholic acid; TDCA, taurodeoxycholic acid; TCA, taurocholic acid; THDCA, taurohydodeoxycholic acid. d Representative current trace of rat P2X2 activated by ATP (10 μM, black bar). Blue bars indicate the application of 20 μM of different bile acids alone