Initiation of hyperpermeability in energy-depleted coronary endothelial monolayers

How the initiation of energy depletion affects macromolecule permeability of a barrier of coronary endothelial cells was investigated. Cultured monolayers of adult rat coronary endothelial cells were exposed to 5 mM KCN and 5 mM 2-deoxy-D-glucose (2-DG). Transendothelial flux of albumin, cellular ATP content, and cytosolic Ca2+ concentration were monitored. Within the first minute, a merely partial loss (28%) of ATP reserves provoked a distinct increase (41%) in albumin flux. Rise of permeability was dependent on Ca2+ release from a thapsigargin- and ATP-sensitive endogenous store, and hyperpermeability was greatly attenuated when energy depletion was extremely rapid, as under sequential addition of 20 mM 2-DG and 5 mM KCN. Attenuation of hyperpermeability could also be achieved by use of 5-20 mM 2,3-butanedione monoxime, an inhibitor of actin-myosin interaction. This finding, together with dependence on Ca2+ and availability of residual energy, indicates that the rapid initiation of hyperpermeability is caused by a contractile mechanism.