GASTROINTESTINAL WATER AND ELECTROLYTES. II. THE EQUILIBRATION OF RADIOPOTASSIUM IN GASTROINTESTINAL CONTENTS AND THE PROPORTION OF EXCHANGEABLE POTASSIUM (Ke) IN THE GASTROINTESTINAL TRACT 1

Gastrointestinal Water and Electrolytes. IV. The Equilibration of Deuterium Oxide (D2O) in Gastrointestinal Contents and the Proportion of Total Body Water (T.B.W.) in the Gastrointestinal Tract1

“…In the preceding three papers of this series we reported the measured amount of sodium, potassium and chloride contained within the lumen of the gut in rabbits and in human subjects at post mortem (4,5,7). The present study is similar in design to these previous experiments and presents observations on a) the amount of intraluminal gastrointestinal water expressed as a fraction of total body water (T.B.W.)…”

“…Data from previous experiments in which the intraluminal content of sodium, potassium, and chloride were determined are summarized in Table VI (4,5,7). The last three columns in Table VI show the calculated concentrations for each of these ions in intraluminal water of stomach, small bowel and large bowel.…”

“…The presence of 14 per cent of Nae, 7 per cent of Ke and 16 per cent of Cle in the contents of the gastrointestinal tract in rabbits has important implications in body partition studies where the normal anatomy of ion distribution or of ion shifts is measured (4,5,7). Calculating the extracellular fluid volume from a chloride space and assuming that all chloride exists in the same concentration as in plasma will lead to significant errors.…”

“…The concept of the anatomy of body water distribution as a two-compartment system consisting of intracellular and extracellular fluid has been shown to be inadequate (1)(2)(3)(4)(5). The heterogeneous nature of the extracellular fluid compartment has been established by previous studies on bone (2), dense connective tissue (6), and transcellular fluid (3)(4)(5).…”

“…The heterogeneous nature of the extracellular fluid compartment has been established by previous studies on bone (2), dense connective tissue (6), and transcellular fluid (3)(4)(5). Cizek (3) has demonstrated that intraluminal gut water is a significant subdivision of body water in a number of species.…”