Duodenal mucosal bicarbonate secretion in man. Stimulation by acid and inhibition by the alpha 2-adrenoceptor agonist clonidine

A multi-channel small diameter tube was used to study the secretion of bicarbonate by 3 cm long segments of the proximal duodenum isolated between balloons. The tube had an outer diameter of 5.3 mm and two central and four smaller, peripheral channels. Measurements of infused phenol red, 14C-PEG and...

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Bibliographic Details
Published in:Gut 1989-12, Vol.30 (12), p.1708-1715
Main Authors: Knutson, L, Flemström, G
Format: Article
Language:English
Subjects:
Adult
Bicarbonates - antagonists & inhibitors
Bicarbonates - metabolism
Clonidine - pharmacology
Duodenum - metabolism
Female
Humans
Hydrochloric Acid - pharmacology
Intestinal Mucosa - metabolism
Male
Middle Aged
Phenolsulfonphthalein
Polyethylene Glycols
Stimulation, Chemical
Vitamin B 12
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Summary:A multi-channel small diameter tube was used to study the secretion of bicarbonate by 3 cm long segments of the proximal duodenum isolated between balloons. The tube had an outer diameter of 5.3 mm and two central and four smaller, peripheral channels. Measurements of infused phenol red, 14C-PEG and vitamin B12 and of trypsin activity were performed to rule out contamination of the perfusate by gastric and pancreatic secretions. Basal secretion of bicarbonate by the duodenal mucosa in healthy subjects varied between 135 and 220 mumol/cm of intestine per hour. Perfusion of the lumen with acid (100 mM HCl for five minutes) increased the secretion to greater than 400 mumol/cm/h and the alpha 2-adrenoreceptor agonist clonidine (150 micrograms iv) decreased the HCO3- secretion by 70 mumol/cm/h. Clonidine simultaneously reduced the mean arterial blood pressure and plasma noradrenaline concentration, but did not affect the plasma glucose or adrenaline concentration. Duodenal bicarbonate secretion is important in the protection of this mucosa against acid discharged from the stomach. Increased sympathetic activity may, by inhibiting the bicarbonate secretion, decrease the protection in proximal duodenum in man and facilitate ulceration.
ISSN:0017-5749
1468-3288
1458-3288
DOI:10.1136/gut.30.12.1708