High glucose modulates albumin permeability across glomerular endothelial cells via a protein kinase C-dependent mechanism.

To investigate the mechanism of glomerular endothelial response to high glucose, an in vitro model of the glomerular endothelial barrier was established in which transfer of fluorescein-labeled albumin across confluent monolayers of immortalized bovine glomerular endothelial cells (GEN) grown on polycarbonate membranes was measured. We first examined the effects of increased concentrations of D-glucose on albumin permeability across GEN monolayers and further investigated the role of protein kinase C (PKC) in the regulation of glucose-induced changes in endothelial barrier function. Incubation with 30 mM D-glucose increased albumin permeability more than those with 10 mM D-glucose. Albumin permeability incubated with 10 mM D-glucose plus 20 mM mannitol was not significantly different from those with 10 mM D-glucose, indicating that the increase in albumin permeability induced by 30 mM D-glucose was not due to high osmolar stimuli. A protein kinase C (PKC) inhibitor, H-7 (25 microM) significantly reduced the permeability-increasing effects of D-glucose. Lactate dehydrogenase release from endothelial cells was not significantly increased above baseline after incubation with 10 mM or 30 mM D-glucose. These results suggest that elevated concentrations of glucose activates PKC, resulting in an increase in albumin permeability across GEN.