Changes in the blood brain barrier in acute hepatic coma

The level of primary insult on the brain in hepatic coma has usually been assumed to be a direct toxic effect on the neural elements. This experiment was designed to investigate the possibility that the blood brain barrier (BBB) in hepatic encephalopathy might be altered. Wistar rats were subjected to a 2 stage hepatectomy. At the first operation, the portal vein was banded with cellophane tape in the hilum of the liver, and the inferior vena cava was ligated above the renal veins. Two mth later, after the development of portosystemic collaterals, a bloodless, total hepatectomy was performed. The rats were then maintained by the infusion of a 5% glucose solution containing 50 mEq/liter of NaCl, at a constant rate of 1.25 ml/hr. It was found that inulin, sucrose, and L glucose are 3 nondiffusible substances that are not transported across the intact BBB. In hepatic coma, however, they cross the BBB in increased amounts. The independent transport systems for pyruvate and L phenylalanine appear to be maintained in the comatose rat. There is the suggestion that the transport of D glucose is depressed, but not eliminated in hepatic encephalopathy. The histologic correlate of these findings in coma was swelling of the astrocytes and pericapillary vacuolation, at least part of which was in the astrocytic foot processes.