The Effect of Atropine on Secretin Release and Aspirated Bicarbonate Secretion after Duodenal Acidification in Man

Abstract

The effect of duodenal instillation of hydrochloric acid on peripheral plasma immunoreactive secretin (IRS) concentration—without or with a constant intravenous infusion of atropine—was studied in eight healthy volunteers. Without atropine infusion, IRS increased from 1.2 ± 0.3 pmol/l to a peak value of 17.1 ± 4.4 pmol/l. The volume of duodenal aspirates increased from 0.74 ± 0.12 ml/min to 5.03 ± 0.46 ml/min, and the bicarbonate output from 7.6 ± 1.7 μmol/min to 349 ± 39 μmol/min. With atropine infusion (bolus of 500 μg + 750 μg/h of atropine sulphate), IRS increased from 1.4 ± 0.3 pmol/l to 14.8 ± 3.6 pmol/l. The volume of the duodenal aspirates increased from 0.71 ± 0.08 ml/min to 2.76 ± 0.37 ml/min and the bicarbonate output from 4.0 ± 1.6 μmol/min to 142 ± 33 μmol/min. The integrated IRS response to acidification was 18% lower during atropine infusion (p < 0.05). Both the aspirated flow rate from the duodenum and the bicarbonate output were markedly reduced by atropine infusion, 45% and 59%, respectively (p < 0.005).

Key-words:

• Acidification
• duodenal
• atropine
• basal secretion
• bicarbonate
• cholinergic reflex
• duodenal aspiration
• man
• pancreatic secretion
• radioimmunoassay
• recovery studies
• secretin