ENHANCED PERMEABILITY TO HORSERADISH PEROXIDASE ACROSS CEREBRAL VESSELS IN THE RAT AFTER PORTOCAVAL ANASTOMOSIS

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Abstract
The blood—brain barrier to horseradish peroxidase (HRP) was examined in rats 10 or 30 days after establishing an end‐to‐side portocaval anastomosis. An increased number of vesicles containing HRP were seen in the endothelial cells of arterioles and to a lesser degree in the endothelial cells of venules and capillaries. Peroxidase was not found in the interendothelial space between tight junctions, which were everywhere intact. The basement membranes of vessels and the neuropil adjacent to these could contain the tracer. Astrocytic endfeet were swollen 10 days after the operation and contained only a few organelles. Thirty days after the operation reactive changes seemed to occur in astrocytes, indicated by less swelling and enhanced number of organelles. The cytoplasm of the astrocytes in some instances was evenly stained by reaction product. A similar staining was very occasionally observed in a few neuronal processes. It is concluded that an increased vesicular transport of HRP is inferred to have occurred across cerebral endothelium in animals after PCA and that the astrocytes may be especially sensitive to damage to the plasma membrane during liver shunt encephalopathy leading to intra‐cellular uptake of substances from the extracellular space.