Endothelial surface charge: blood-brain barrier opening to horseradish peroxidase induced by the polycation protamin sulfate.

Perfusion of rat brain with the polycation protamin sulfate caused a decrease in the stainability of luminal surface of cerebral endothelium to positively charged colloidal iron. This change reflecting a decrease in the anionic sites of the endothelial plasma membrane was accompanied by opening of the blood-brain barrier to horseradish peroxidase. The polyanion heparin reversed colloidal iron binding but failed to prevent permeability alteration of the cerebral endothelium.