COMPARISON OF D2O AND ETHANOL DILUTIONS IN TOTAL-BODY WATER MEASUREMENTS IN HUMANS

Total body water was measured by ethanol dilution and D2O stable isoto pe dilution in a group of 20 healthy volunteers (5 females and 15 male s), predominantly 23- to 31-year-old students. Both indicator substanc es were given orally with an ethanol burden of 0.8 g/kg body weight an d a D2O burden of 0.1 g/kg body weight after 12-h food and fluid restr iction. This first direct comparison of total body water (TBW) from et hanol and D2O dilutions revealed the ethanol compartments to be smalle r than those of D2O. The quotient of TBW (ethanol)/TBW (D2O) was 97.7% ,which is the order of the quotient TBW ((H2O)-O-18)/TBW (D2O) ( = 97% ), well known from the literature and taken to represent relatively ex actly the value of TBW overestimation (based on H/D exchange for acid protons) following D2O dilution [36]. Thus the value of TBW (ethanol) is almost identical to that of (H2O)-O-18, which provides direct evide nce that ethanol is distributed only in the body water.