Exposure to free fatty acid increases the transfer of albumin across cultured endothelial monolayers.

An initial exposure to high concentrations of free fatty acid increased the transfer of albumin across cultured endothelial monolayers. The rate and amount of albumin transfer was dependent on the oleic acid concentration to which the cultures were initially exposed, with 300 microM producing the maximum transfer. The albumin transfer also increased with the increasing time of exposure to oleic acid, the maximum effect occurring during the first 24 hours. An exposure to 300 microM linoleic acid produced an even greater increase in albumin transfer than did 300 microM oleic acid. The increased albumin transfer observed when cells were exposed to high concentrations of free fatty acid was largely reversible after reincubation of the cell monolayers in free fatty acid-poor media. In parallel experiments, radioactive oleic acid incorporation into cell triglycerides increased linearly as the fatty acid concentration was raised, with cell triglyceride content increasing up to sevenfold after incubation in a medium containing 300 microM oleic acid. A significant amount of oleic acid was incorporated into phospholipids, and the fatty acid composition of the endothelial triglycerides and phospholipids was modified. All these effects of oleic occurred without altering the incorporation of leucine into the cell protein. These results indicate that exposure to high concentrations of free fatty acid can alter endothelial cell lipid composition, and that this increases the albumin transfer across endothelium. This process might permit more macromolecules to enter the arterial wall.