A compartmental analysis of ²⁴Na kinetics in rat cerebrum, sciatic nerve and cerebrospinal fluid

Abstract

SUMMARY1. The kinetics of 24Na exchange in rat cerebrospinal fluid, brain and sciatic nerve were studied during steady-state plasma isotope conditions. The entrance of 24Na into brain and sciatic nerve was found to fit a three compartmental model. Using newly derived equations for compartmental analysis, the first compartment 24Na 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 tj for compartmental equilibration between plasma and brain ECS was 2 hr and from ECS to intracellular space 14 hr; in nerve the respective ti's were i 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 tj's for plasma-c.s.f. 24Na 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 24Na radioactivity from ventricle to cortex.

Graphical Evaluation of Blood-to-Brain Transfer Constants from Multiple-Time Uptake Data

“…This results in a significant advantage for data analysis in comparison to compartmental analysis, since the results for any compartmental analysis are highly specific for the particular compartmental model chosen. An illustration of this problem is provided by Levin and Patlak (1972). These authors used two different compartmental models and pro duced two different sets of transfer numbers from their data.…”

Selection of Experimental Conditions for the Accurate Determination of Blood — Brain Transfer Constants from Single-Time Experiments: A Theoretical Analysis

“…However, the results from any compartmental analysis of experimental data are highly specific for the particular com partmental model chosen. Levin and Patlak (1972) demonstrated this limitation by obtaining two dif ferent sets of transfer numbers from an analysis of their data by two different compartmental models.…”

Effect of acute serum depletion on Na+ ‐K+ homeostasis in cultured human skin fibroblasts

“…To further examine the effect of FBS removal, we calculated the parameters of a serial, three-compartmental model (Levin and Patlak, 1972). The pool sizes of a three-compartmental model in parallel were also calculated as given by Smith et al (1979).…”