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A compartmental analysis of 24 Na kinetics in rat cerebrum, sciatic nerve and cerebrospinal fluid
Author(s) -
Levin Victor,
Patlak Clifford S.
Publication year - 1972
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.1972.sp009913
Subject(s) - sciatic nerve , compartment (ship) , cerebrospinal fluid , chemistry , extracellular , ventricle , intracellular , anatomy , extracellular fluid , kinetics , biophysics , medicine , physics , biology , biochemistry , oceanography , quantum mechanics , geology
1. The kinetics of 24 Na exchange in rat cerebrospinal fluid, brain and sciatic nerve were studied during steady‐state plasma isotope conditions. The entrance of 24 Na into brain and sciatic nerve was found to fit a three compartmental model. Using newly derived equations for compartmental analysis, the first compartment 24 Na space of brain was found to be about 22% and the second compartment space about 6%; the corresponding sciatic nerve spaces were 26 and 11%, respectively. In the discussion, arguments are presented that suggest that the first compartment is the extracellular space (ECS) and the second compartment is the intracellular space. The t ½ for compartmental equilibration between plasma and brain ECS was 2 hr and from ECS to intracellular space 14 hr; in nerve the respective t ½ 's were ⅔ hr and 10 hr. 2. A third compartment of 18% was found in sciatic nerve which was interpreted to be anatomically confined to the epi‐ and perineurium; in brain the corresponding space was 2% and was felt to be anatomically and kinetically an inactive closed compartment in parallel with the blood. 3. There were two t ½ 's for plasma‐c.s.f. 24 Na equilibration of less than 10 min and 2 hr. 4. Profiles of brain, from cortex to ventricle, at 6 min, demonstrated a gradient of decreasing 24 Na radioactivity from ventricle to cortex.