F-ACTIN CYTOSKELETON AND SUCROSE PERMEABILITY OF IMMORTALIZED RAT-BRAIN MICROVASCULAR ENDOTHELIAL-CELL MONOLAYERS - EFFECTS OF CYCLIC-AMP AND ASTROCYTIC FACTORS

The immortalised RBE4 cell line, derived from rat brain capillary endo thelial cells, preserves many features of the in vivo brain endotheliu m, and hence is of interest as a potential in vitro model of the blood -brain barrier (BBB). This study reports the effects of elevated intra cellular cAMP and factors released by astrocytes on the F-actin cytosk eleton and paracellular sucrose permeability of monolayers of RBE4 cel ls. RBE4 cells grown in control medium showed a marked increase in the F-actin staining at the cytoplasmic margin at confluence, which was n ot significantly enhanced by elevation of intracellular cAMP and/or ad dition of astrocyte-conditioned medium (ACM). The formation of the mar ginal band of F-actin was accompanied by an increase in the F-actin co ntent of the RBE4 cells up to confluence, and a decline in F-actin con tent thereafter. Elevation of intracellular cAMP or co-culture above a strocytes significantly decreased the paracellular sucrose permeabilit y of confluent RBE4 cell monolayers grown on collagen filters (P < 0.0 1 and P < 0.001, respectively). Go-culture above astrocytes together w ith elevated cAMP also produced a significant decrease in the sucrose permeability of the monolayer(P < 0.01) but this was no greater than w ith astrocytes alone. These findings show that the RBE4 cell line may serve as a useful in vitro model for the study of brain endothelial ce ll physiology and agents which alter the permeability of the BBB. (C) 1997 Elsevier Science B.V.