Release of VIP, secretin and motilin after duodenal acidification in man.

Plasma VIP, secretin and motilin were measured in 9 volunteers following intraduodenal instillation of 50 ml of 0.1 mol/1 HCl over 3 minutes. VIP rose from 1.7 +/- 0.7 pmol/1 to a peak at 6 minutes of 6.6 +/- 0.9 pmol/1 and was still significantly elevated at 30 minutes. By comparison the elevation of secretin was more transitory rising from a basal value of 2.5 +/- 0.4 pmol/1 to a peak of 10 +/- 1.5 pmol/1 at 3 minutes and returning to baseline by 10 minutes. The rise of motilin, from a higher baseline, was intermediate in pattern, from 23 +/- 7 pmol/1 basally to a 4 minute peak of 40 +/- 10 pmol/1. Thus the elevation of VIP was the most longlasting, and while probably not of sufficient magnitude to stimulate pancreatic bicarbonate secretion via the circulation, could reflect a significant local role in regulating the response of the intestinal mucosa to acid.