Figure 6

Dipyridamole does not amplify suppression of markers of the HPA axis in vitro. (a) AtT-20 corticotroph cells were pretreated with dipyridamole (Dp; 10 μmol/l) or rolipram (Rol; 10 μmol/l) as indicated. Cells were stimulated with corticotropin-releasing factor (CRF) or vehicle control before quantitating cAMP levels. Error bars are + standard deviation (SD). *P < 0.01 versus CRF alone. (b) AtT-20 cells were pretreated with Dp or control for 24 hours. Medium was refreshed with compounds, and then stimulated with CRF or vehicle control for an additional 3 hours. Medium was collected for determination of ACTH levels by ELISA. Error bars are + SD. *P < 0.001 versus CRF + Dp. (c) AtT-20 cells were pretreated with increasing doses of prednisolone in the absence (grey curve) or presence (black curve) of Dp (10 μmol/l) for 24 hours. Medium was refreshed with compounds plus CRF. After 3 hours, ACTH levels were determined by ELISA. *P < 0.001 versus vehicle alone. (d) AtT-20 cells were incubated with increasing doses of prednisolone in the absence (grey curve) or presence (black curve) of Dp for 24 hours. POMC mRNA levels were determined by RT-PCR analysis, using β-actin as the endogenous control. Dp alone (10 μmol/l) and vehicle control responses are indicated with an open triangle and circle, respectively. Error bars are ± SD, and statistical analysis is by analysis of variance with Tukey. HPA, hypothalamus-pituitary-adrenal.