Carotid artery constriction in acute hypertension.

The effects of carotid artery constriction on cerebrovascular ultrastructure and permeability in acute hypertension have been assessed. The right common carotid artery of 26 male Wistar-Kyoto normotensive rats was constricted with a silver wire clip. Forty-eight hours later these animals received an angiotensin amide injection (1 microgram/kg body weight) or infusion for 3--4 hours (0.5 or 1.7 microgram/min/kg body weight) or were subjected to subdiaphragmatic aortic constriction. All animals were injected with horseradish peroxidase (HRP) (20 mg/100 g body weight) and sacrificed after 5--15 minutes. Parietal cortex from both hemispheres was processed for light and electron-microscopic examination. The arterial vessels of the right hemisphere from animals given injections of or infused with angiotensin II exhibited increased permeability to HRP, as manifested by the presence of reaction product in interendothelial cell clefts, in subendothelial space, in endothelial and smooth muscle cell pinocytotic vesicles, and along smooth muscle cell basal laminas. In contrast, no alterations in the permeability of ipsilateral vessels were seen in rats with aortic constriction. Cerebral cortical arterial vessels from the left hemisphere in all groups of animals exhibited segmental dilatation and constriction and abnormal permeability to HRP. The results suggest that angiotensin administration can produce increased permeability of cerebral cortical vessels in the absence of elevated blood pressure.