Early changes in blood-brain barrier permeability after porto-caval shunt and liver ischaemia

The brain oedema, distribution space (DS) and brain uptake index (BUI), of L-glucose, inulin, B12 vitamin and of three polypeptidic hormones of increasing molecular weight (angiotensin-I, gastrin and insulin) were measured in the rat after sham operation, porto-caval shunt (PCS) or liver ischaemia. At an early stage following PCS or liver ischaemia brain oedema was not constant, and was only demonstrable after liver ischaemia in a large number of animals. Substances without an active transport and with a low diffusion coefficient such as L-glucose and inulin had a very low BUI, unchanged even if the 3H2O brain content or the DS were modified. B12 vitamin, DS and BUI were very high and did not change after liver ischaemia or PCS. Insulin DS and BUI were low in the three groups of animals, whereas it decreased after PCS for gastrin. A significant increase of BUI and DS (without any cerebral oedema) was demonstrated for angiotensin-I, a polypeptidic hormone of molecular weight 1300. This polypeptidic marker is in the same range of MW as the preliminary recently recognized medium-sized molecules which may be involved in the pathogenesis of encephalopathy during experimental acute liver failure. However, not only the MW, but the nature of such polypeptides may be of importance in the genesis of this limited impairment of BBB permeability.