FIGURE 6.

Inhibition of Na⁺ currents in GFP(+) cells by rRA2 is partially mediated by UTP. A, characteristic time course recordings of whole-cell Na⁺ currents in a GFP(+) H441 cell pretreated with either A77-1726 (20 μm, solid circles) or vehicle (0.1% DMSO, open circles) for 12 h, infected with rRA2 (m.o.i. = 1), and patched 3 days later. The cells were held at -40 mV, and currents were elicited by a step pulse to -60 mV every 0.5s. The cells were perfused with amiloride (amil., 10 μm) as indicated. Pretreatment with A77-1726 partially restored amiloride sensitivity. Notice the lack of amiloride (amil.)-sensitivity in cells treated with vehicle (open circles). B, mean values ± S.E. of basal (solid) and amiloride-sensitive (striped bars) current densities at -60 mV for non-inoculated H441 cells incubated with A77-1726 (20 μm, n = 5) for 3 days and GFP(+) cells incubated with either DMSO (n = 5) or A77-1726 (20 μm, n = 6) 3 days after rRA2 infection. (p < 0.05 (^*) and p < 0.01 (^**) are from their corresponding non-inoculated values). C and D, α (C) and β (D) ENaC mRNA levels in non-inoculated (solid bars), GFP(-)(diagonal bars), and GFP(+)(cross-hatched bars) cells treated by DMSO or A77-1726 (20 μm). ENaC mRNA levels of each cell group were measured by real-time RT-PCR from cells sorted and collected by flow cytometry 3-5 days after rRA2 infection and then divided by those of the non-inoculated cells (m.o.i. = 1; ^**, p < 0.01 compared with non-inoculated cells; data are from four independent experiments).