Comparative Metabolism of Tritiated Water by Mammals

Tritiated water was used to measure the volume and turnover of exchangeable body water in 7 species of adult mammals. Using these parameters, the daily turnover of exchangeable body water was calculated for each species. Body water content was about 60% of body weight for all species. Biological half- times for turnover of body water varied from 1.1 days for mice to 9.5 days for man. The longest biological half-time observed was about 12 days for desert Kangaroo rats (Dipodomys deserti). Values for the volume and turnover of body water for the various species are compared with values reported in the literature. An interspecies correlation of the power function type between daily water turnover and species weight was established. Body water turnover was found to vary as the 0.80 power of body weight for all species except the desert rat. A parabolic interspecies correlation was also established between total body water and total body solids for the 7 species. The relative partition of water and solids in adult mammals is constant with a value of 1 when expressed interspecifically. (auth)