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Title: Can tritiated water-dilution space accurately predict total body water in chukar partridges

Total body water (TBW) volumes determined from the dilution space of injected tritiated water have consistently overestimated actual water volumes (determined by desiccation to constant mass) in reptiles and mammals, but results for birds are controversial. We investigated potential errors in both the dilution method and the desiccation method in an attempt to resolve this controversy. Tritiated water dilution yielded an accurate measurement of water mass in vitro. However, in vivo, this method yielded a 4.6% overestimate of the amount of water (3.1% of live body mass) in chukar partridges, apparently largely because of loss of tritium from body water to sites of dissociable hydrogens on body solids. An additional source of overestimation (approximately 2% of body mass) was loss of tritium to the solids in blood samples during distillation of blood to obtain pure water for tritium analysis. Measuring tritium activity in plasma samples avoided this problem but required measurement of, and correction for, the dry matter content in plasma. Desiccation to constant mass by lyophilization or oven-drying also overestimated the amount of water actually in the bodies of chukar partridges by 1.4% of body mass, because these values included water adsorbed onto the outside of feathers. When desiccatingmore » defeathered carcasses, oven-drying at 70 degrees C yielded TBW values identical to those obtained from lyophilization, but TBW was overestimated (0.5% of body mass) by drying at 100 degrees C due to loss of organic substances as well as water.« less
Authors:
; ;
Publication Date:
OSTI Identifier:
5739152
Resource Type:
Journal Article
Resource Relation:
Journal Name: J. Appl. Physiol.; (United States); Journal Volume: 5
Country of Publication:
United States
Language:
English
Subject:
59 BASIC BIOLOGICAL SCIENCES; WATER; BODY COMPOSITION; BIRDS; BODY FLUIDS; ERRORS; MEASURING METHODS; TRITIUM OXIDES; ANIMALS; BIOLOGICAL MATERIALS; CHALCOGENIDES; HYDROGEN COMPOUNDS; LABELLED COMPOUNDS; MATERIALS; OXIDES; OXYGEN COMPOUNDS; TRITIUM COMPOUNDS; VERTEBRATES 551001* -- Physiological Systems-- Tracer Techniques