Effect of the D5 receptor on Na+–K+ ATPase activity in HEK293 cells heterologously expressing the D5 receptor. (a) Concentration-response of Na+–K+ ATPase activity caused by fenoldopam (10−10–10−6 mol/l), a D1-like receptor agonist, for 15 min. Results in this experiment are expressed as percent change from control (n = 6, *P < 0.01 vs. control, ANOVA, Duncan's test). (b) Time-dependent response (5–30 min) of Na+–K+ ATPase activity caused by fenoldopam (10−7 mol/l). Results in this experiment are expressed as percent change from control (n = 7, *P < 0.01 vs. control, ANOVA, Duncan's test). ANOVA, analysis of variance.