Effect of Intraduodenal Bile and Taurodeoxycholate on Exocrine Pancreatic Secretion and on Plasma Levels of Vasoactive Intestinal Polypeptide and Somatostatin in Man

Intraduodenal (i.d.) application of bile or Na-taurodeoxycholate
(TDC) dose dependently enhances basal exocrine pancreatic
secretion. The hydrokinetic effect is mediated at least in part by
secretin. This study should show, whether vasoactive intestinal
polypeptide (VIP), a partial agonist of secretin, may also be
involved in the mediation of the hydrokinetic effect. Furthermore,
plasma concentrations of somatostatin-like immunoreactivity (SLI)
were measured in order to check whether this counterregulating
hormone is also released by bile and TDC. Twenty investigations
were carried out on 10 fasting healthy volunteers provided with a
double-lumen Dreiling tube. Bile and TDC were intraduodenally
applied in doses of 2-6 g and 200-600 mg, respectively, at 65-min
intervals. Plasma samples were withdrawn at defined intervals for
radioimmunological determination of VIP and SLI. Duodenal juice was
collected in 10-min fractions and analyzed for volume, pH,
bicarbonate, lipase, trypsin, and amylase. I.d. application of bile
or TDC dose dependently stimulated hydrokinetic and ecbolic
pancreatic secretion. Bile exerted a slightly stronger effect than
TDC. Pancreatic response was simultaneously accompanied by a
significant increase of plasma VIP and SLI concentrations. The
effect of bile on integrated plasma VIP and SLI concentrations
seems to be dose dependent; the effect of TDC on integrated SLI,
too. For the increase of integrated plasma VIP concentrations after
TDC no dose-response relation could be established. We conclude
that VIP may be a further mediator of bile-induced volume and
bicarbonate secretion. The release of plasma SLI indicates that
inhibitory mechanisms concomitantly are triggered by i.d. bile and
TDC, as already shown during digestion for the intestinal phase of
pancreatic secretion.