Macromolecule permeability of coronary and aortic endothelial monolayers under energy depletion

The dependence of macromolecule permeability (MP; indicator fluorescein isothiocyanate-labeled albumin) of endothelial cells on their energetic state was investigated using confluent monolayers of rat coronary microvascular endothelial cells and porcine aortic macrovascular endothelial cells. When oxidative and glycolytic energy productions were inhibited (5 mM KCN plus 5 mM 2-deoxy-D-glucose) 90% of the endothelial ATP contents were lost within 15 min, followed by a progressive increase of MP, disintegration of the actin cytoskeleton, and the opening of intercellular gaps. Elution of the blocker and a subsequent 3-h incubation in complete culture medium reversed the effects of 2-h metabolic blockade, completely for MP and partially for ATP levels. Coronary microvascular and aortic macrovascular endothelial cells responded similarly to energy depletion and repletion, the microvascular cells being more sensitive. The results demonstrate that 1) energetic inhibition augments endothelial macromolecule permeability when both oxidative and glycolytic energy production are inhibited, 2) increased macromolecule permeability in energy-depleted endothelial monolayers is caused by the opening of intercellular gaps, and 3) endothelial cells reversibly tolerate up to 2 h of almost complete ATP depletion.