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

Abstract

The effect of duodenal instillation of HCl on peripheral plasma immunoreactive secretin (IRS) concentration without or with a constant i.v. infusion of atropine, was studied in 8 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 .mu.mol/min to 349 .+-. 39 .mu.mol/min. With atropine infusion (bolus of 500 .mu.g + 750 .mu.g/h of atropine, sulfate), 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 .mu.mol/min to 142 .+-. 33 .mu.mol/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).