Gastrointestinal Water and Electrolytes. III. The Equilibration of Radiobromide in Gastrointestinal Contents and the Proportion of Exchangeable Chloride (Cle) in the Gastrointestinal Tract1

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Abstract
Intraluminal gastrointestinal chloride content was measured in rabbits and in human subjects studied post mortem. In the former, gut chloride was referred to Cle estimated with KBr82, while in the latter gut chloride was referred to the predicted Cle values. Total exchangeable chloride averaged 34.9 [plus or minus] 3.5 meq per kg of body weight in rabbits. Of this, 16.0 [plus or minus] 4.5% was in the lumen of the gastrointestinal tract, with 11.7 [plus or minus] 4.4% in the stomach, 2.5 [plus or minus] 0.7% in the small intestine, and 1.7 [plus or minus] 0.4% in the cecum and proximal half of the large intestine. Radiobromide exchange equilibrium was complete to within 10% for all segments of the gastroinestinal tract 48 hours after injection. No significant difference in either the Cle or the quantity of intraluminal gastrointestinal chloride was found between male and female rabbits. Human subjects at post-mortem examination had relatively small amounts of intraluminal gastrointestinal chloride; the mean values were 1.9% of the predicted Cle in the "total" gastrointestinal tract, with 0.91% in the stomach, 0.67% in the small intestine, and 0.32% in the cecum and proximal transverse colon. The quantity of intraluminal chloride in normal man cannot be reliably inferred from these data. The implications of these data are discussed in terms of the dynamics of chloride transport across the gastrointestinal mucosa and the anatomy of body chloride.