A non-invasive method to study evolution of extracellular fluid volume in mice using time domain nuclear magnetic resonance.

We examined the feasibility of monitoring mice ECF by a non-invasive method, using time-domain nuclear magnetic resonance (TD-NMR). This technique allows differentiating protons in a liquid environment (free fluid) from protons in soft tissues containing a majority of either small molecules (lean) or large molecules (fat). Moreover, this apparatus enables rapid, non-invasive, and repeated measurements on the same animal. We assessed the feasibility of coupling TD-NMR analysis to a longitudinal metabolic cage study by monitoring mice daily. We determined the effect of a 24-hour water deprivation on mice body parameters and detected a sequential and overlapping decrease in free fluid and lean mass during water deprivation. Finally, we studied the effect of mineralocorticoids that are known to induce a transient increase in the ECF but for which no direct measurements have been performed in mice. We showed for the first time that mineralocorticoids induce a transient ~15% increase in free fluid in conscious mice. TD-NMR is therefore the first method to allow direct measurement of discrete changes in the ECF in conscious small animals. This method allows analysis of kinetic changes to stimuli prior to investigating with terminal methods and will allow further understanding of fluid disorders. PMID: 32475134 [PubMed - as supplied by publisher]
Source: Am J Physiol Renal P... - Category: Urology & Nephrology Authors: Tags: Am J Physiol Renal Physiol Source Type: research