EFFECTS OF ENERGY DEPRIVATION-INDUCED BY FLUOROCITRATE IN IMMORTALIZED RAT-BRAIN MICROVESSEL ENDOTHELIAL-CELLS

The effects of the mitochondrial aconitase inhibitor, fluorocitrate on the immortalised rat brain endothelial cell line (RBE4) were investig ated. Treatment with different concentrations of fluorocitrate (0-1 mM ) for 24 h induced a significant, concentration-dependent decrease in the MTT reduction (an index of mitochondrial function), intracellular ATP content, glucose consumption and lactate production by RBE4 cell m onolayers but did not alter the glucose to lactate ratio at concentrat ions lower than 0.5 mM. At all concentrations, fluorocitrate induced a significant decrease in the protein content per well. Fluorocitrate t reatment of confluent RBE4 cells induced a marked redistribution of th e F-actin cytoskeleton from a characteristic marginal band to a more d iffuse cytosolic pattern. This redistribution of the cytoskeleton coin cided with a reduction in the total cellular F-actin content of the RB E4 cells at fluorocitrate concentrations greater than 0.5 mM. Treatmen t of confluent RBE4 cells with fluorocitrate had no significant effect on RBE4 cell monolayer permeability measured by FITC-dextran or [C-14 ]sucrose. These results show that whilst energy deprivation following fluorocitrate treatment induces significant changes in the RBE4 cell F -actin cytoskeleton and cellular metabolism, it does not have any sign ificant effect on endothelial cell monolayer permeability. These resul ts demonstrate that profound toxic effects on endothelial cell structu re and metabolism are not necessarily accompanied by changes in endoth elial cell monolayer permeability.