Fig. 1.

Selective stimulation of the P2Y₂ receptor in principal cells decreases epithelial Na⁺ channel (ENaC) activity. A: gap-free current trace of ENaC activity in a cell-attached patch on the apical plasma membrane of a principal cell in a split-open aldosterone-sensitive distal nephron from a C57BL/6 mouse. The tubule was isolated from a mouse maintained on a Na⁺-free diet for 1 wk. The patch was voltage clamped to −60 mV with downward inward current, and the closed state current level is denoted by a dashed line. The patch contained ≥7 ENaC. The trace shows time points before and after addition of 1 μM MRS2768 (arrow) to the extracellular bath solution. For the purpose of presentation, the trace was filtered at 40 Hz and slight corrections were made to baseline to adjust for slow current drifts. B: means ± SE (black circles) and individual data points (gray circles) for ENaC activity [open channel probability (NP_o; where N is the number of channels in a patch and P_o is the probability that these channels are open)] from experiments in tubules treated with vehicle (n = 11 from 3 different mice) or MRS2768 (n = 8 from 3 different mice) for 30 min before being patched. Mice of both sexes were used in approximately equal proportions. *Significantly lower than vehicle (by two-tailed t-test).