Division of Nephrology, University of Utah Health Sciences Center, Salt Lake City, Utah 84132, USA.
Am J Physiol Renal Physiol. 2010 Jul;299(1):F280-3. doi: 10.1152/ajprenal.00113.2010. Epub 2010 May 12.
Conventional indicator dilution techniques for measuring body fluid volume are laborious, expensive, and highly invasive. Bioimpedance spectroscopy (BIS) may be a useful alternative due to being rapid, minimally invasive, and allowing repeated measurements. BIS has not been reported in mice; hence we examined how well BIS estimates body fluid volume in mice. Using C57/Bl6 mice, the BIS system demonstrated <5% intermouse variation in total body water (TBW) and extracellular (ECFV) and intracellular fluid volume (ICFV) between animals of similar body weight. TBW, ECFV, and ICFV differed between heavier male and lighter female mice; however, the ratio of TBW, ECFV, and ICFV to body weight did not differ between mice and corresponded closely to values in the literature. Furthermore, repeat measurements over 1 wk demonstrated <5% intramouse variation. Default resistance coefficients used by the BIS system, defined for rats, produced body composition values for TBW that exceeded body weight in mice. Therefore, body composition was measured in mice using a range of resistance coefficients. Resistance values at 10% of those defined for rats provided TBW, ECFV, and ICFV ratios to body weight that were similar to those obtained by conventional isotope dilution. Further evaluation of the sensitivity of the BIS system was determined by its ability to detect volume changes after saline infusion; saline provided the predicted changes in compartmental fluid volumes. In summary, BIS is a noninvasive and accurate method for the estimation of body composition in mice. The ability to perform serial measurements will be a useful tool for future studies.
传统的指示剂稀释技术用于测量体液容量既繁琐又昂贵，而且具有高度侵入性。生物阻抗谱（BIS）可能是一种有用的替代方法，因为它快速、微创，并且允许重复测量。BIS 尚未在小鼠中报道；因此，我们研究了 BIS 如何在小鼠中估算体液容量。使用 C57/Bl6 小鼠，BIS 系统在体重相似的动物之间，全身水（TBW）、细胞外液（ECFV）和细胞内液体积（ICFV）的总体间变异<5%。TBW、ECFV 和 ICFV 在体重较重的雄性和体重较轻的雌性小鼠之间存在差异；然而，TBW、ECFV 和 ICFV 与体重的比值在小鼠之间没有差异，并且与文献中的值非常接近。此外，在 1 周内重复测量表明<5%的个体内变异。BIS 系统使用的默认电阻系数是为大鼠定义的，它产生的 TBW 体成分值超过了小鼠的体重。因此，使用一系列电阻系数在小鼠中测量体成分。将大鼠定义的电阻值降低 10%，可以提供 TBW、ECFV 和 ICFV 与体重的比值，与通过常规同位素稀释获得的比值相似。通过盐水输注后检测体积变化来进一步评估 BIS 系统的灵敏度；盐水提供了预期的各腔体液体积变化。总之，BIS 是一种非侵入性和准确的估计小鼠体成分的方法。进行连续测量的能力将是未来研究的有用工具。
