PDE inhibitors increase sensitivity of CEM cells to glucocorticoid, with concurrent elevation of cAMP.

(A) CEM cells were cultured with 40 μg/mL aminophylline, 40 μg/mL dyphylline, or 20 μM rolipram in the presence of various concentrations of dexamethasone. (B) CEM cells were cultured with 20 μM forskolin and 20 μM rolipram, each alone and in combination, with various concentrations of dexamethasone. MTT assay measurements are expressed as a viability ratio of drug-treated cells to untreated control cells in each experiment. Error bars represent SD ranges for each data point. (C) CEM cells were cultured with combinations of forskolin, rolipram, and 1 μM dexamethasone for 30 minutes, and total cellular cAMP was measured. Cellular cAMP is expressed as a ratio compared to untreated cells and plotted on a logarithmic scale. Error bars represent SD.