Studies of Body Water and Water Turnover Determined with Deuterium Oxide Added to Food

Abstract

Abstract In 5 dogs which ingested 25 or 50 ml. of D2O with one daily meal, maximal plasma concentrations of tracer were reached in 12-24 hr. The disappearance rate during 14 days was exponential, confirming studies of others in humans. Water turnover, calculated from values obtained for body water and the disappearance rates, agreed well with total water intake, which included water taken as such and that derived by oxidation. Water intake per square meter of surface area varied widely; there was also no constant relationship between either total turnover or extrarenal loss and caloric intake. Since animals were maintained at nearly constant weights for long periods, caloric intake and total heat production were presumably equivalent. Thus the possibility of estimating total heat production from water turnover or extrarenal loss was not promising, but the validity of body water and turnover estimations was well supported. Average value for body water was 60.6% of body weight, with a range of 56.1% to 66.6%.