Abstract
Although the active transport of BS across the terminal ileum has been well documented, analysis of previous studies shows that ileal active transport cannot account for total BS recovery (Am 3 Physiol 244:G507,1983).
To evaluate passive BS absorption in the proximal small intestine, weanling male Sprague-Dawley rats (age 39±4 days; wt 146 ± 26 g - mean ± SD) were anesthetized, the common bile duct was cannulated and the jejunum (J) and ileum (I) were catheterized and isolated. 1 ml of taurocholate (TC) solution in concentrations ranging from 0.5 mM to 10 mM and containing 3H-TC and 14C-polyethylene glycol (PEG - non-absorbable marker) were injected into the J. Bile was collected for 90 min. post-injection and counted. J and I were then ligated (to prevent mixing), divided into 8 segments, homogenized, and counted. TC absorption from the intestine was determined using 14C-PEG as a reference substance. In all animals, >94% of the 14C-PEG marker was found in proximal J (segments 1-3).
A linear correlation was found between the conc. of TC administered and the amount of TC recovered in bile (N=20, r=.91, p<.001). 8.4 ± 2.9 % of the dose was excreted in bile in 90 minutes. The rate of TC absorption was linearly related to TC conc. (N=13, r=.97, p< .001) and was non-saturable.
These findings demonstrate that TC is avidly absorbed by a passive process at physiologic concentrations (8-10 mM) in the proximal small bowel of the rat. When calculated for the entire small bowel, passive absorption accounts for between 54 and 69% of total BS secretion and is the major mechanism of BS conservation. These findings suggest that rapid proximal BS absorption rather than fecal BS loss is the mechanism for decreased intraluminal BS concentration in the neonate.
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Stahl, G., Shiau, YF., Watkins, J. et al. CONTRIBUTION OF PASSIVE PROXIMAL BILE SALT (BS) ABSORPTION TO ENTEROHEPATIC CIRCULATION (EHC) OF BS IN THE RAT. Pediatr Res 18 (Suppl 4), 213 (1984). https://doi.org/10.1203/00006450-198404001-00722
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DOI: https://doi.org/10.1203/00006450-198404001-00722