Total body water distribution of creatinine and urea in nephrectomized dogs

Abstract

It was the purpose of this study to measure and to compare the volumes of distribution of creatinine, urea and tritiated water in nephrectomized dogs. After bilateral nephrectomy a solution containing known amounts of these was infused intravenously and at a constant rate in some studies. Frequent arterial blood samples were taken during and following infusion for periods up to 20 hours and were analyzed for water and the infused substances. The respective volumes of distribution and rates of dilution were calculated. Isotopic water and urea were distributed in 95% and creatinine in 61% of their final volumes of distribution at the end of a 30-minute infusion. Final equilibrium occurred in about 90 minutes with water and urea and in about 4 hours with creatinine. Creatinine became distributed in 99 ± 3% of the tritiated water volume and in 101 ± 5% of the urea volume. Urea distributed in 98 ± 4% of the tritiated water volume. It is concluded that administered creatinine is distributed in total body water of nephrectomized dogs with an equilibrium time of about 4 hours and that urea is similarly distributed within 1 1/2 hours.