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Intracellular water preexchange lifetime in neurons and astrocytes
Author(s) -
Yang Donghan M.,
Huettner James E.,
Bretthorst G. Larry,
Neil Jeffrey J.,
Garbow Joel R.,
Ackerman Joseph J.H.
Publication year - 2018
Publication title -
magnetic resonance in medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.696
H-Index - 225
eISSN - 1522-2594
pISSN - 0740-3194
DOI - 10.1002/mrm.26781
Subject(s) - extracellular , intracellular , extracellular fluid , biophysics , astrocyte , chemistry , neuroscience , microbiology and biotechnology , nuclear magnetic resonance , biology , biochemistry , central nervous system , physics
Purpose To determine the intracellular water preexchange lifetime, τ i , the “average residence time” of water, in the intracellular milieu of neurons and astrocytes. The preexchange lifetime is important for modeling a variety of MR data sets, including relaxation, diffusion‐sensitive, and dynamic contrast–enhanced data sets. Methods Herein, τ i in neurons and astrocytes is determined in a microbead‐adherent, cultured cell system. In concert with thin‐slice selection, rapid flow of extracellular media suppresses extracellular signal, allowing determination of the transcytolemmal‐exchange‐dominated, intracellular T 1 . With this knowledge, and that of the intracellular T 1 in the absence of exchange, τ i can be derived. Results Under normal culture conditions, τ i for neurons is 0.75 ± 0.05 s versus 0.57 ± 0.03 s for astrocytes. Both neuronal and astrocytic τ i s decrease within 30 min after the onset of oxygen‐glucose deprivation, with the astrocytic τ i showing a substantially greater decrease than the neuronal τ i . Conclusions Given an approximate intra‐ to extracellular volume ratio of 4:1 in the brain, these data imply that, under normal physiological conditions, an MR experimental characteristic time of less than 0.012 s is required for a nonexchanging, two‐compartment (intra‐ and extracellular) model to be valid for MR studies. This characteristic time shortens significantly (i.e., 0.004 s) under injury conditions. Magn Reson Med 79:1616–1627, 2018. © 2017 International Society for Magnetic Resonance in Medicine.