Rosiglitazone potentiates the PACAP-induced cAMP increase. A and B, Effect of rosiglitazone (500 nm), PACAP (300 nm), or the combination of both on the cAMP accumulation. Calu-6 cells were incubated for 16 h with the above mentioned substances and without (A) or with the PPARγ antagonist GW9662 (1 μm) (B). Cells were incubated for additional 15 min with the PDE inhibitor IBMX (100 μm) where indicated. C, Rosiglitazone is not an AC activator. Effect of rosiglitazone (500 nm), PACAP (300 nm), or the combination of both on AC activity. Calu-6 cells were incubated for 5 min with the above mentioned substances after a 15-min preincubation with 100 μm IBMX. Under these conditions, the cAMP accumulation is directly proportional to AC activity. D, The potentiation of the PACAP-induced cAMP increase by rosiglitazone requires intact transcription. Effect of rosiglitazone (500 nm), PACAP (300 nm), or the combination of both on the cAMP levels in the presence of the transcriptional inhibitor actinomycin D (10 μm). Calu-6 cells were incubated for 16 h with the indicated substances. Rosi, Rosiglitazone. The data shown are means ± sem; *, P < 0.05 relative to control; #, P < 0.05 relative to the corresponding cAMP level in the absence of IBMX; **, P < 0.05 as indicated. NS, Not significant.