ADA inhibits 8Cl-AMP activity. MM.1S cells are treated with 8Cl-AMP for 5 days at the indicated concentrations in the presence (light bars) or absence (dark bars) of 2 U/mL of ADA. The assay is done in normal growth medium that does not contain serum. 8Cl-cAMP (5 μmol/L) and 8Cl-AD (5 μmol/L) are included as controls. Cell number is assayed and presented as described in Materials and Methods.