Phagocytosis of erythrocytes in the subarachnoid space at spinal nerve exits.

After intracisternal injection of heparinised autologous blood in cats, spinal nerve exits (SNE) of the subarachnoid space (SAS) were examined by scanning and transmission electron microscopy. Phagocytes, erythrocytes and erythrophages (= macrophages which had phagocytosed red blood cells) were found at SNE. Some lining cells of the SAS had retracted from the adjacent cells and had rounded up. Cells which formed an integral part of the subarachnoid lining cells also had phagocytosed erythrocytes. Debris of an exhausted erythrophage was phagocytosed by other macrophages. Finally the observation has been made that erythrophages are capable of leaving the SAS actively by migrating through the layer of lining cells, thus getting into the leptomeningeal connective tissue space.