Rate of Passage of Water through Capillary and Cell Walls

The Measurement of Total Body Water in the Human Subject by Deuterium Oxide Dilution

“…It will be appreciated, however, that the "D space" or "total exchangeable hydrogen" is about 0.5-1.5%7 of body weight larger than total body water. Reasoning on the basis of similar data Hevesy and Jacobsen (41) estimated the exchangeable hydrogen to have a water equivalent of 0.5-2.0%o of the body weight. This is of little moment in body water measurement but is of course of great importance in considering D uptake or synthesis into organic substances.…”

The Use of the Mass Spectrometer to Measure Deuterium in Body Fluids 1

“…In order to obtain a high order of accuracy we have used the mass spectrometer in the measurement of deuterium concentration in body fluids. In The inherent error in the method, i.e., the loss of deuterium by exchange, has been estimated as having a water equivalent of 0.5% to 2.0%o of the body weight and is probably close to 1.0% to 1.5% (3,13,14,15). Thus, for the average adult, results calculated by the D20 method are too high by an estimated 700-1,000 ml.…”

“…The primary inherent source of error in this method lies in the exchange of deuterium atoms with labile hydrogen atoms of organic molecules (12)(13)(14). Since exchange occurs rapidly (13,14) and represents only a small loss of deuterium from the water stores (3,13,14,15), it does not affect the general validity of the method.…”

The Active Transport of Water in Living Systems

“…The relative constancy of the plasma volume is remarkable when it is considered in relation to the rate of transpiration of fluid through the capillary walls. Hevesy & Jacobsen (1940) found that the apparent volume of distribution of deuterium oxide half a minute after it had been injected into the jugular vein of a rabbit was about equal to the total volume of the extracellular fluids, whilst in 10 min. the deuterium oxide was almost equally distributed throughout all the water in the body.…”