Captopril (SA333) is a potent and specific inhibitor of peptidyl-dipeptidase A. It blocks the conversion of angiotensin I to angiotensin II, a vasoconstrictor and important regulator of arterial blood pressure.

Binding assay: Cells are plated in 24-well plates and cultured until confluence. Before the experiment, the cells are washed three times with 0.5 mL per well of DMEM at room temperature. After removal of the medium, 400 μL binding DMEM is added and the plate is then left for 15 min at 37 ℃. For saturation binding assays cells are incubated with increasing concentrations [3H]Candesartan (final concentrations between 0.15 nM and 15 nM) in a final volume of 0.5 mL at 37 ℃ for 5 min to 180 min. For competition binding assays 50 μL of buffer or 50 μL of buffer containing increasing concentrations of unlabelled Candesartan is added. After 30 min, 50 μL of buffer containing [3H]Candesartan (final concentration 1.1 nM) or [3H]Candesartan (final concentration 1.0 nM) is added, and the cells are further incubated for 30 min at 37 ℃.