Abstract #0511

DEXSY can measure water exchange linked to cellular homeostasis and active states in central nervous system tissue

Nathan H. Williamson^1,2, Rea Ravin¹, Teddy X. Cai^1,3, Melanie Falgairolle⁴, Michael J. O'Donovan⁴, and Peter J. Basser¹

¹National Institute of Child Health and Human Development, Potomac, MD, United States, ²National Institute of General Medical Sciences, Potomac, MD, United States, ³Department of Clinical Neurosciences, Wellcome Centre for Integrative Neuroimaging, FMRIB, University of Oxford, Oxford, United Kingdom, ⁴National Institute of Neurological Disorders and Stroke, Potomac, MD, United States

Synopsis

We propose a new functional MR method based on steady-state transmembrane water exchange rate measurements with diffusion exchange spectroscopy (DEXSY). Rapid DEXSY methods are implemented on a low-field MR system with a strong static gradient to test for an active component of water exchange in ex vivo neonatal mouse spinal cords. Temperature-dependent Arrhenius activation energies for water exchange are significantly greater in viable “live” samples than in the same samples after fixation, suggesting a connection to ATP-driven enzymatic processes. Moreover, exchange rates in live samples significantly decrease after blocking Na⁺/K⁺-ATPase pump activity, revealing an active component of water exchange.

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