Transactivation activity of the wild type and mutant MRs. HEK-293T cells transiently expressing the MR, MRN770A, MRA773G, MRQ776A, MRS810A, MRS810M, MRR817A, MRM852A, MRC942A, MRT945A, or MRA773G/S810M were incubated for 16 h with aldosterone (Aldo), 18-vinyl-4-pregnen-3,18,20-trione (18OVP), or spironolactone (Spiro). The cell extracts were assayed for luciferase and β-galactosidase activities as reported previously (30). The GraphPad Prism software was used for curve fitting and calculation of the EC50 values.