Abstract
Endothelial cells of the cerebral arterial system in spontaneously hypertensive rats were investigated by scanning electronmicroscopy and found to show progressive changes such as increased microvilli, numerous plasmalemmal pits, enlargement of the cells and well-developed marginal folds. Regressive changes, such as balloon-like protrusions and crater-like cave-ins, were also observed. Platelet adhesion to the injured endothelial surface of cerebral arteries was frequent. The significance of these changes in the development of hypertensive cerebrovascular lesions is discussed.