Comparative metabolism of tritiated water by macropodid marsupials.
The total body-water content (TBW) and rate of water turnover were measured usingtritiated water in five species of macropodod marsupials (kangaroos), which ranged in weight from 1 to 50 kg.  Animals fitted with rumen cannulas were used to estimate the time required for tritiated water to equilibrate within the body of large kangaroos.  In hydrated kangaroos this was 6 h, during the time 2.7% of the injected tritiated waterwas lost from the body.  During dehydration, the equilibrium time was extended to 10h. Values up to 78% of body weight were found for TBW in the larger species of kangaroo, and these values were similiar to those found for other ruminantlike mammals, particularly those with a low body-fat content.  The smaller macropodids had a TBW (about 60% of body weight) similiar to that of most laboratory mammals.  The rates of waterturnover of the macropodids were related to body weights by the expression 1/day = 0.09kg-0.80.  Macropodid marsupials have a daily water usage shich is about two-thirds ofthat found for eitherians and this may be related to the lower metabolic rate of marsupials.
D000273:Adipose Tissue; D000818:Animals; D001834:Body Water; D001835:Body Weight; D003681:Dehydration; D007614:Macropodidae / Q000378:metabolism; D008394:Marsupialia / Q000378:metabolism*; D013997:Time Factors; D014316:Tritium; D014867:Water / Q000378:metabolism*
D014867:Water; D014316:Tritium