Oxidant-induced endothelial leak correlates with decreased cellular energy levels

A common finding in oxidant-induced organ injury is loss of vascular endothelial cell (EC) integrity and subsequent leak. The mechanisms involved are unclear, but maintenance of EC structure and functional integrity is highly dependent on the EC energy level. This study investigates whether oxidant-induced EC injury and concomitant increased monolayer permeability correlate with decreased energy levels. Rabbit pulmonary microvascular EC in vitro were exposed to varying levels of glucose oxidase as an oxidant-generating source for 2 h. Permeability changes were determined by albumin-Evans blue dye exclusion by monolayers of EC. ATP (nm/10(6) cells) and energy charge [ATP + 1/2ADP/(ATP + ADP + AMP)] were determined by HPLC. ATP and energy charge were found to decrease as permeability increased in response to increasing glucose oxidase concentration. ATP levels were a significantly more sensitive predictor of increased permeability than was energy charge. At 24 h, both permeability and ATP levels returned toward baseline. It appears that cell energy charge is preserved despite significant increases in monolayer permeability.