Endothelial barrier function is partly regulated by the transcellular transport of albumin and other macromolecules via endothelial caveolae. The main structural protein in caveolae is caveolin-1, that forms a scaffold around caveolae.

Here we show that thrombin induces an increase in uptake of albumin in human endothelial cells by about 20%. To investigate the role of caveolin-1 in albumin uptake, we have generated caveolin-1 negative cells from caveolin-1 deficient mice. We found that caveolin-1 -/- cells display a 3-fold higher uptake of FITC-labeled albumin compared to wild type cells. After reexpression of caveolin-1 in caveolin-1 -/- cells by lentiviral gene transfer, the albumin uptake was reduced to levels observed in wildtype cells. This data shows that caveolin-1 negatively controls the uptake of albumin in endothelial cells.