Fig. 5. Influence of elevated cAMP levels on barrier permeability. BCEC monolayers were incubated as indicated with medium or with medium containing PT (200 ng/ml) and/or CT (1 µg/ml) and/or forskolin (50 µM) for 4 hours. The transendothelial HRP transport was assessed by measuring HRP concentrations spectrophotometrically in the lower compartment. OD values were taken as a measure for the traversed HRP indicating the relative permeability. The standard deviations (error bars, n=6) are indicated.