TY - JOUR
T1 - Effect of extracellular volume on the energy stored in transmembrane concentration gradients
AU - Maex, Reinoud
N1 - © 2021 American Physical Society. This is the accepted manuscript version of an article which has been published in final form at https://doi.org/10.1103/PhysRevE.104.044409
PY - 2021/10/15
Y1 - 2021/10/15
N2 - The amount of energy that can be retrieved from a concentration gradient across a membrane separating two compartments depends on the relative size of the compartments. Having a larger low-concentration compartment is in general beneficial. It is shown here analytically that the retrieved energy further increases when the high-concentration compartment shrinks during the mixing process, and a general formula is derived for the energy when the ratio of transported solvent to solute varies. These calculations are then applied to the interstitial compartment of the brain, which is rich in and ions and poor in . The reported shrinkage of this compartment, and swelling of the neurons, during oxygen deprivation is shown to enhance the energy recovered from NaCl entering the neurons. The slight loss of energy on the part of can be compensated for by the uptake of ions by glial cells. In conclusion, the present study proposes that the reported fluctuations in the size of the interstitial compartment of the brain (expansion during sleep and contraction during oxygen deprivation) optimize the amount of energy that neurons can store in, and retrieve from, their ionic concentration gradients.
AB - The amount of energy that can be retrieved from a concentration gradient across a membrane separating two compartments depends on the relative size of the compartments. Having a larger low-concentration compartment is in general beneficial. It is shown here analytically that the retrieved energy further increases when the high-concentration compartment shrinks during the mixing process, and a general formula is derived for the energy when the ratio of transported solvent to solute varies. These calculations are then applied to the interstitial compartment of the brain, which is rich in and ions and poor in . The reported shrinkage of this compartment, and swelling of the neurons, during oxygen deprivation is shown to enhance the energy recovered from NaCl entering the neurons. The slight loss of energy on the part of can be compensated for by the uptake of ions by glial cells. In conclusion, the present study proposes that the reported fluctuations in the size of the interstitial compartment of the brain (expansion during sleep and contraction during oxygen deprivation) optimize the amount of energy that neurons can store in, and retrieve from, their ionic concentration gradients.
UR - http://www.scopus.com/inward/record.url?scp=85117705664&partnerID=8YFLogxK
U2 - 10.1103/PhysRevE.104.044409
DO - 10.1103/PhysRevE.104.044409
M3 - Article
SN - 1539-3755
VL - 104
JO - Physical Review E
JF - Physical Review E
IS - 4
M1 - 044409
ER -