Scanning and transmission electron microscopic study on the cerebral arterial endothelium of experimentally hypertensive rats fed an atherogenic diet.

In order to clarify the roles of hypertension and hypercholesterolemia in atherogenesis, the cerebral arterial endothelium of experimentally hypertensive female rats fed an atherogenic diet were investigated by scanning and transmission electron microscopy. The hypertension was induced by constriction of the bilateral renal arteries. In both hypertensive groups, group I (hypertension + hypercholesterolemia) and group III (hypertension), many endothelial cells covered with numerous microvillous projections were observed. Pinocytotic vesicles and caveolae were also increased in these endothelial cells. On the other hand, in group II loaded with only hypercholesterolemia, microvillous projections on the endothelial cells tended to be increased, but its grade seemed to be lower than those of the hypertensive groups. These findings suggest that hypertension appears to be more effective than hypercholesterolemia in the cause of the increase of microvilli on the endothelial cell surfaces and the increase may be related to increased permeability in the cerebral arteries.