An electron microscope study on permeability in cerebral venules in the rats with hypertensive encephalopathy

Hypertensive encephalopathy was induced in the rat by clipping one renal artery and contralateral nephrectomy. The possible changes of vascular permeability of the cerebral blood capillaries and venules were investigated by using ferritin as a tracer. The uninephrectomized rats served as controls. In controls, ferritin was never seen in the basement membranes, within plasmalemmal vesicles on the basal surface of the endothelium, or in endothelial cell junctions of cerebral capillaries and venules up to 180 min after the injection. In venules of the brain in rats with hypertensive encephalopathy, a number of ferritin particles appeared in the basement membrane in 60 min after the injection. Many plasmalemmal vesicles in the endothelial cells of venules were labeled with ferritin. However, ferritin particles were never found in the endothelial cell junctions. The results suggested that leakage of macromolecules, such as serum proteins, occurred in venules mainly by increased vesicular transport.