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

taurodeoxycholate (TDC) dose dependently enhances basal exocrine pancreatic secretion. The hydrokinetic ef-fect 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 immunoreac-tivity (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 fast-ing 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 Plasma samples were withdrawn at defined in-tervals for radioimmunological determination of VIP and SLI.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. 1.d. application of bile or TDC dose depen-dently stimulated hydrokinetic and ecbolic pancreatic se-cretion. Bile exerted a slightly stronger effect than TDC. Pancreatic response was simultaneously accompanied by a significant increase of plasma VIP and SLI concentra-tions. 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 inte-grated 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 in-dicates that inhibitory mechanisms concomitantly are triggered by i.d. bile and TDC, as already shown during digestion for the intestinal phase of pancreatic secretion. Key Words: Bile-Duodenum-Pancreatic secretion-Somatostatin-Taurodeoxycholate-Vasoactive intesti