A noninvasive method to study regulation of extraceullular fluid volume in rats using nuclear magnetic resonance.

A NONINVASIVE METHOD TO STUDY REGULATION OF EXTRACEULLULAR FLUID VOLUME IN RATS USING NUCLEAR MAGNETIC RESONANCE. Am J Physiol Renal Physiol. 2015 Dec 23;:ajprenal.00405.2015 Authors: Gordon CJ, Phillips P, Johnstone AF Abstract Time domain nuclear magnetic resonance (TD-NMR)-based measurement of body composition of rodents is an effective method to quickly and repeatedly measure proportions of fat, lean, and fluid without anesthesia. TD-NMR provides a measure of free water in a living animal, termed percent fluid, and is a measure of unbound water in the vascular and extracellular spaces. We hypothesized that injecting a bolus of fluid into the peritoneal cavity would lead to an abrupt increase in %fluid and the rate of clearance monitored with TD-NMR would provide a noninvasive assessment of the free water homeostasis in an awake rat. Several strains of laboratory rats were injected intraperitoneally with 10 ml/kg isotonic or hypertonic saline and %fluid was monitored repeatedly with a Bruker "Minispec" TD-NMR body composition system. Following isotonic saline, %fluid increased immediately by 0.5% followed by a recovery over ~6 hr. Injecting hypertonic (3X normal saline) resulted in a significantly greater rise in %fluid and longer recovery. IP and subcutaneous fluid injection led to similar rates of clearance. The Wistar Kyoto rat strain displayed significantly slower recovery to fluid loads compared to Long-Evans and Sprague-Dawl...
Source: Am J Physiol Renal P... - Category: Urology & Nephrology Authors: Tags: Am J Physiol Renal Physiol Source Type: research