Figure 3.

Example application of the NMR/BIS method, with acute volume depletion by furosemide. A: body mass assessed by electronic balance immediately before, and at 10, 30, and 60 min after acute intraperitoneal injection of 100% dimethylsulfoxide (DMSO) or furosemide, 10 mg/kg, delivered via injection of 30 mg/mL furosemide dissolved in 100% DMSO solution at 0.33 µL/g body mass. Drug × time interaction P < 0.0001. B: fat-free mass, determined by TD-NMR. Drug × time interaction P < 0.0001. C: cumulative urine mass. Drug × time interaction P = 0.0002. D: change in total body water (TBW), calculated as 73.2% of fat-free mass as determined by TD-NMR. Drug × time interaction P < 0.0001. E: change in NMR/BIS-corrected extracellular fluid (ECF) mass. F: change in NMR/BIS-corrected intracellular fluid (ICF) mass. G: ratio of ECF/ICF. H: comparison of TBW mass as determined at time 0 by TD-NMR, and 60 min postinjection by TD-NMR and by desiccation. For A–H, DMSO n = 8 and furosemide n = 8 male C57BL/6J mice purchased at 10 wk of age from the Jackson Laboratories, aged to 12 wk and maintained on 2920X chow diet. Data are presented as means ± SE and were analyzed using two-way repeated-measures ANOVA followed by Sidak’s multiple-comparisons procedure. *P < 0.05 between treatment groups at indicated timepoint, by Sidak’s multiple-comparisons procedure. BIS, bioimpedance spectroscopy; ECF, extracellular fluid; ICF, intracellular fluid; NMR, nuclear magnetic resonance; TD-NMR, time-domain nuclear magnetic resonance.