Kinetics of Deuterium in Dogs Following Intravenous Administration of Deuterium Oxide

The Primary Study for Measurement of Canine Body Fat Mass by Deuterium Oxide Dilution Method

Abstract

Obesity is becoming popular in companion dogs, and for its diagnosis and therapy, assessment of adiposity is essential. Deuterium oxide (D₂O) dilution method is established as one of the most reliable methods to estimate body fat content in humans, and this method was also applied to dogs in anesthesia (Burkholder et al.,1998). The purpose of this study is to determine the precondition for repeated measurement of body fat mass by the D₂O dilution method, in conscious dogs. Three conscious and unrestrained beagles were intravenously injected with D₂ Oat 0.2 ml/kg BW, and then their plasma were corrected at 15,30,60,90,120 and 180 minutes after the injection. Plasma samples were purified by vacuum sublimation, and their deuterium concentrations were measured by gas chromatographic method. The concentration of plasma deuterium had already reached a plateau level at 15 minutes and was not significantly changed until 180 minutes. It suggests that in conscious dogs, only 15 min is adequate time for D₂O equilibration, to correct plasma in body fat measurement by D₂O dilution method. Their body fat contents obtained by the method were 18,23 and 39%, which adequated their Body Condition Score (BCS),3,3 and 4, respectively. The plasma deuterium concentration was further measured at 3,7,14,28,49 and 70 days after the injection. It decreased to 36 and 74% of the plateau level at Day 3 and 7, respectively, and returned to pre-injection level at Day 49. These results indicate that the turnover rate of body water is about 4 days in dogs, and that at least a 7-week interval is required for the repeated measurement by D₂O dilution method.