PENETRATION OF SMALL MOLECULAR-WEIGHT SUBSTANCES THROUGH CULTURED BOVINE BRAIN CAPILLARY ENDOTHELIAL-CELL MONOLAYERS - THE EARLY EFFECTS OFCYCLIC ADENOSINE-3',5'-MONOPHOSPHATE

Second messengers, such as cyclic adenosine 3',5'-monophosphate (cAMP) , have been shown to take part in the regulation of blood-brain barrie r permeability. In the present study, elevation of cAMP levels decreas ed sucrose (mol. wt, 342) and inulin (mol. wt, 5000) permeability acro ss monolayers of bovine brain capillary endothelial cells as early as 1 h after exposure. Since both tracers use predominantly a paracellula r pathway, we assume that cAMP may increase the tightness of the tight junctions through protein phosphorylation.