Body Water Content and Turnover in Several Species of Rodents as Evaluated by the Tritiated Water Method

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Abstract
Body water content and turnover were determined on 80 rodents, representing 12 species, using the tritiated water method. All experimental rodents were maintained under similar laboratory conditions. Measurements of body water content indicated wide variability in the degree of body fatness. Mean values of body fat as a percentage of body weight ranged from 3.0 to 38.8 per cent for the 12 species. The equation, WTR = n (LBM)b, was used to relate water transfer rate (WTR) to lean body mass (LBM). The overall exponent (b) for 12 species of rodents equaled 0.78 ± 0.044 (standard deviation) and represents the interspecies estimate. The exponent computed for three species of the genus Microtus equaled 0.69 ± 0.093. Specific water transfer rates ranged from 0.34 to 1.76 (ml/g0,69)/d. In general, water transfer rates were correlated with water availability in the natural habitat of each species. Species inhabiting moist areas had high specific water transfer rates while species inhabiting arid regions had lower specific water transfer rates.