Fig. 7.

Expression of wild-type RhAG or of RhAG F65S upregulates Na⁺/K⁺ ATPase activity in Xenopus oocytes. A: ⁸⁶Rb⁺ influx into Xenopus oocytes expressing wild-type RhAG, RhAG F65S, AE1 E758K, or AE1 S731P was sensitive to inhibition by ouabain (500 μM) and bumetanide (5 μM). Wild-type AE1 served as a negative control for ⁸⁶Rb⁺ influx (67, 68). 10 ng cRNA was injected for all constructs. H₂O-corrected values are means ± SE for (n) oocytes. *P < 0.05 compared with wild-type RhAG (Student's unpaired t-test). B: reproduction of data in A, with magnified y-axis scale showing ⁸⁶Rb⁺ influx insensitive to ouabain + bumetanide, emphasizing that wild-type RhAG and its F65S mutant increase ⁸⁶Rb⁺ “leak” flux insensitive to ouabain and bumetanide. *P < 0.05 compared with wild-type RhAG. C: inhibition of RhAG-associated ⁸⁶Rb⁺ influx by 0.5 mM ouabain alone, by 5 μM bumetanide alone, and by the combination. D: 3 days′ incubation of oocytes coexpressing RhAG and GPB in high K⁺ bath (gray bars) significantly reduced ⁸⁶Rb⁺ influx sensitive to inhibition by ouabain + bumetanide (compare y-axis values to A and C). Black bars indicate 3 days' incubation in ND-96.