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Uptake of 36 Cl and 22 Na by the Brain‐Cerebrospinal Fluid System: Comparison of the Permeability of the Blood‐Brain and Blood‐Cerebrospinal Fluid Barriers
Author(s) -
Smith Quentin R.,
Johanson Conrad E.,
Woodbury Dixon M.
Publication year - 1981
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1981.tb05298.x
Subject(s) - cerebrospinal fluid , extracellular fluid , blood–brain barrier , extracellular , chemistry , fluid compartments , biophysics , central nervous system , pathology , biology , endocrinology , medicine , biochemistry
Transport and permeability properties of the blood‐brain and blood‐CSF barriers were determined by kinetic analysis of radioisotope uptake from the plasma into the CNS of the adult rat. Cerebral cortex and cerebellum uptake curves for 36 Cl and 22 Na were resolved into two components. The fast component ( t ½ 0.02–0.05 h, fractional volume 0.04–0.08) is comprised of the vascular compartment and a small perivascular space whereas the slow component ( t ½ 1.06–1.69 h, fractional volume 0.92–0.96) represents isotope movement across the blood‐brain barrier into the brain extracellular and cellular compartments. Uptake curves of both 36 Cl and 22 Na into the CSF were also resolved into two components, a fast component ( t ½ 0.18 h, fractional volume 0.24) and a slow component ( t ½ 1.2 h, fractional volume 0.76). Evidence suggests that the fast component represents isotope movement across the blood‐CSF barrier, i.e., the choroid plexuses, whereas the CSF slow component probably reflects isotope penetration primarily from the brain extracellular fluid into the CSF. The extracellular fluid volume of the cerebral cortex and cerebellum was estimated as ˜13% from the initial slope of the curve of brain space versus CSF space curve for both 36 Cl and 22 Na. Like the choroid plexuses, the glial cell compartment of the brain appears to accumulate Cl from 2 to 6 times that predicted for passive distribution. The relative permeability of the blood‐CSF and blood‐brain barriers to 36 Cl, 22 Na, and [ 3 H]mannitol was determined by calculating permeability surface‐area products (PA). Analysis of the PA values for all three isotopes indicates that the effective permeability of the choroidal epithelium (blood/CSF barrier) is significantly greater than that of the capillary endothelium in the cerebral cortex and cerebellum (blood‐brain barrier).