Figure 1. Effect of elevated cAMP on barrier integrity. Changes in paracellular permeability in response to TNF-α (20 ng/ml; T) with or without co-treatment with 10 µM forskolin (F) and 50 µM rolipram (R) were determined by quantifying the flux of FITC-dextran (10 kDa) across cells grown on porous culture inserts. Treatment with TNF-α for 20 h significantly increased the flux of dextran in comparison to untreated cells (Control). Co-treatment with F and R [i.e., TNF-α+F+R)] significantly attenuates the (TNF-α)-induced increase in permeability. Each bar represents mean±SEM of eight independent trials; * and ** denote p<0.001 when comparing the TNF-α-treated group with the control group and the (TNF-α+F+R)-treated group with the TNF-α-treated group, respectively.