Duodenal mucosal bicarbonate secretion in humans: a brief review.
Level 5 - mechanism / opinion, no new human data
Narrative review summarizing human physiological perfusion experiments
PubMed 3103203 · doi:10.3109/00365528609093825
What was done
The author reviewed human physiological studies measuring bicarbonate secretion using a validated perfusion method that isolates 4-cm segments of proximal or distal duodenum free of gastric, pancreatic, and biliary secretions. The review examined baseline secretion rates as well as responses to luminal hydrochloric acid (HCl), synthetic prostaglandin E1, chloride substitution with Na2SO4, and vasoactive intestinal polypeptide (VIP).
What was found
At rest, the healthy human proximal duodenum produced approximately 175 µmol/cm-h (approximately 700 µmol/h for a 4-cm duodenal bulb), while the distal duodenum produced approximately 25 µmol/cm-h. HCl produced a prompt and sustained increase in bicarbonate output in both segments, demonstrating a proximal-to-distal gradient. Synthetic prostaglandin E1 produced a dose-related increase in output, VIP significantly increased proximal output, and substitution of NaCl perfusate with Na2SO4 produced a brief decrease in bicarbonate output.
Why it matters
This review quantifies resting and stimulated human duodenal mucosal bicarbonate secretion, establishing its role as a primary defensive mechanism against gastric acid.
Limits
The abstract describes a narrative review and does not state sample sizes, subject characteristics, exact p-values, or measures of variance. Clinical endpoints and pathological states such as duodenal ulceration were not evaluated in the reported data.
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