An Electron Microscope Study of Hypertensive Encephalopathy in the Rat with Renal Hypertension

Abstract

The brain of rats in which hypertensive encephalopathy was induced by means of constriction of the main renal artery was examined under the electron microscope.The most remarkable changes in the brain were swelling of perivascular astrocytes and an enlargement of the extracellular spaces. The latter was confined only to the white matter. These findings were compatible with those of the “vasogenic type” of brain edema as described by KLATZO.A remarkable increase in the number of pinocytotic vesicles and caveolae intracellulares was noticed in the endothelial cells of capillaries and venules. Marginal vacuoles were frequently encountered in the endothelium. Tight junctions between the endothelial cells of capillaries and venules appeared intact. The present study suggested that the vesicular transport in the capillaries and venules plays an important role in conveying edema fluid through capillary walls to brain tissues. The increased pinocytotic activity was thus conceived to represent one factor causing brain edema at least in hypertensive encephalopathy.