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The Blood-Brain Barrier

Volume 89 of the series Methods in Molecular Medicine™ pp 133-144

Blood-Brain Barrier Permeability Using Tracers and Immunohistochemistry

  • Sukriti NagAffiliated withDivision of Neuropathology, University of TorontoToronto Western Research Institute, University Health Network

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Abstract

The first report of blood-brain barrier (BBB) permeability by Paul Ehrlich (1) involved the use of the exogenous tracer Coerulean-S as described in Chapter 6. Over the years, tracers of different sizes were introduced to study the permeability properties of normal cerebral vessels in physiologic and pathologic states (Table 1). Tracers provide information about the permeability status of vessels immediately before sacrifice. The disadvantage of exogenous tracers is that there are side effects associated with the administration of some tracers in live animals. The properties and methods by which some of these tracers are used to study BBB permeability to proteins and ions in pathologic states will be described.
Table 1

The Exogenous Tracers Used to Detect Blood-Brain Barrier Permeability and the Methods to Detect Endogenous Protein Extravasations

I. Exogenous Tracers

1. Markers of Protein Permeability

Dyes: Evans blue

Fluorescent Tracers:

Fluorescein isothiocynate-dextran (MW: 62,000)

Fluorescein isothiocynate-albumin (MW: 67,000)

Horseradish peroxidase* (MW: 40,000)

Microperoxidase* (MW: 1900)

Radiolabeled Compounds

125Idine-labeled serum albumin

14C-labeled dextran (MW: 70,000)

2. Markers of Solute and Ion Permeability

Ionic Lanthanum* (MW: 138.9)

Sodium Fluorescein (MW: 376)

Lucifer Yellow (MW: 457)

Ruthenium Red* (MW: 800)

Fluorescein isothiocynate-dextran (MW: 3000)

Radio-labeled Compounds

14C-α -Aminoisobutyric acid (MW 103)

14C Sucrose (MW: 342)

14C- Methotrexate (MW: 455)

14C-Inulin (MW: 5000)

II.Endogenous Protein Extravasation

Detected of Plasma Proteins by Immunohistochemistry

Immunoperoxidase

Immunofluorescence

Immunogold technique

The molecular weights of the tracers are expressed in Daltons.

*Exogenous tracers detectable with EM.