ASCORBIC-ACID STIMULATES BARRIER FUNCTION OF CULTURED ENDOTHELIAL-CELL MONOLAYER

The macromolecular permeability of cultured bovine aortic, bovine veno us, and human umbilical vein endothelial cell monolayers was decreased significantly in culture medium containing L-ascorbic acid (Asc Acid; 0.01-0.1 mM) and L-ascorbic acid 2-phosphate (Asc 2-P). Dithiothreito l, which shows reducing activity equivalent to that of Asc Acid, did n ot affect endothelial permeability. Asc Acid induced a sixfold increas e in collagen synthesis by the endothelial cells. The coexistence of L -azetidine 2-carboxylic acid, an inhibitor of collagen synthesis, atte nuated the effect of Asc 2-P in a dose-dependent manner. Another colla gen synthesis inhibitor, ethyl-3,4-dihydroxybenzoate, also inhibited c ollagen synthesis and increased endothelial permeability. The decrease in permeability of the endothelial monolayer was dependent on a reduc tion of the permeability coefficient of the endothelial monolayer. The se findings indicate that endothelial barrier function is stimulated b y Asc Acid via an increase in collagen synthesis. (C) 1995 Wiley-Liss, Inc.