Cerebral endothelial surface charge in hypertension.

Anionic groups on cerebral arteriolar endothelium were localized using cationized ferritin (CF), and alterations in the distribution of these groups were documented in arterioles with increased permeability to horseradish peroxidase (HRP) in angiotensin-induced acute hypertension. Normotensive animals showed a uniform distribution of anionic groups on the endothelial luminal plasma membrane when fixed or live vessels were reacted with CF. Anionic groups were localized at the mouth of pinocytotic vesicles in both preparations; however, only live cells demonstrated CF particles within vesicles, and the possibility that these represent pinocytosed CF particles cannot be ruled out. Cationized ferritin particles were not observed on the plasma membranes within interendothelial spaces in either of the preparations. Sixty percent of hypertensive animals with pressures over 200 mmHg showed increased arteriolar permeability to HRP. At 2.5 min, permeable arteriolar segments with active vesicular transport of HRP showed marked reduction or loss of CF binding. Capillaries and venules in the adjacent cortex and nonpermeable arterioles demonstrated linear endothelial CF binding similar to controls. Most permeable vessels of animals killed 6-20 min after onset of acute hypertension when the blood-brain barrier is usually closed showed CF binding on endothelium indicating that there is rapid restoration of the net negative charge. These studies demonstrate that increased arteriolar permeability in acute hypertension is associated with a transient alteration of surface charge. The mechanism by which charge is altered remains to be determined.