Observations on Penetration of Serum Proteins into the Central Nervous System

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This chapter presents the studies on penetration of serum proteins into the central nervous system. The observations are derived from experiments on cats in vivo and on isolated chick and rabbit choroid plexuses using human and bovine albumin and y-globulin labeled with fluorescein isothiocyanate, 125I and 13lI. The permeability of the normal cerebral vasculature to serum proteins was ascertained by injecting cats intravenously with fluorescein labeled albumin (FLA) and fluorescein labeled γ-globulin (FLGG). Two distinct degrees of an increased permeability of cerebral vessels to fluorescein labeled albumin were seen after the intracarotid injection of hypertonic glucose. Observations on the local cold injury to the cerebral cortex showed an extensive migration of extravasated protein tracers using the white matter as their preferential pathway. Observations on the passage of protein conjugates from the cerebrospinal fluid suggested that serum proteins do not penetrate directly through the pial lining into the brain parenchyma. Observations on protein penetration into the isolated chick choroid plexus indicated the presence of an active transport mechanism that may be responsible for the stromal uptake of fluorescein labeled albumin. The role of glia in relation to the penetration of serum proteins into the nervous tissue is also discussed in the chapter.