Permeability of intracranial blood vessels to endogenous serum albumin.

The blood-brain barrier to endogenous serum albumin labeled with Evans blue was studied by standard fluorescence microscopic techniques in cats. Systematic studies confirm that, except in certain well-known loci (hypothalamic median eminence, subfornical organ, area postrema, etc.), blood vessels within brain tissue are impermeable to endogenous albumin. But studies also demonstrate that in virtually all arteries at the base and over the surface of the brain and brain stem, labeled albumin passes readily through endothelium and the vascular wall to the adventitia. These observations are discussed in the context of current concepts of intracranial vascular permeability and, in terms of general biology, the possible consequences of the permeability to serum albumin of intracranial, extraparenchymal blood vessels on the composition and physiology of cerebrospinal fluid and in the pharmacokinetics of antibiotics, anticonvulsants, and antineoplastic and vasoactive agents.