The use of tritiated water, 4-aminoantipyrene and N-acetyl-4-aminoantipyrene for the measurement of body water in living pigs.

I . Body water content was estimated in sixteen pigs at each of three weights 27.55 and go kg with tritium, 4-aminoantipyrene (4-AA) and N-acetyl-4-aminoantipyrene (NAAP). The values obtained were compared with chemical analysis of the whole carcass. 2. The tritium method estimated total body water content accurately at 27 kg live weight but overestimated it by approximately 10% at both 55 and 90 kg live weight. 3. Antipyrene was eliminated from the pig at a rate of 55 %/h and could not be used for body water estimations. 4. Measurements with NAAP on nine pigs tended slightly to underestimate total body water content. Estimates with 4-AA showed no association with the values obtained by chemical analysis.