BIS is an interesting, objective method to support clinical DWA. Further studies should be performed to investigate beneficial clinical effects of this approach.

To evaluate the physiological role of cholecystokinin (CCK) in humans, we studied the influence of the specific CCK receptor antagonist loxiglumide (CR 1505) on gallbladder contraction, pancreatic enzyme output, plasma CCK concentrations, mouth-to-cecum transit time (MCTT), stool weight, and fecal fat excretion. Infusion of CCK-8, producing CCK plasma levels of 10-12 pmol/l, decreased gallbladder volume to 21% of the initial volume (P less than 0.01) and increased bilirubin output 8- to 10-fold and pancreatic enzyme secretion 2- to 4-fold. Infusion of loxiglumide (10 mg.kg-1.h-1 iv) abolished CCK-8-stimulated enzyme and bilirubin output. Basal gallbladder volume increased 68% during loxiglumide infusion (P less than 0.001) and 137% (P less than 0.001) after 7 days of oral loxiglumide treatment (3 x 1.6 g/day). Gallbladder contraction and bilirubin output in response to the intraduodenal instillation of a liquid meal (382 kcal) was completely inhibited by loxiglumide; gallbladder volume even increased 45% postprandially during loxiglumide infusion (P less than 0.02) and 145% after long-term loxiglumide treatment (P less than 0.001). Meal-stimulated pancreatic enzyme output was diminished 46-53% after acute and 25-29% after chronic administration of loxiglumide. Meal-stimulated integrated plasma CCK-immunoreactive (CCK-ir) concentrations, determined by RIA, were 3.2-fold higher during loxiglumide infusion (P less than 0.02); plateau CCK levels were markedly elevated (10.1 +/- 1.4 vs. 3.7 +/- 0.5 pM). Plasma CCK-like bioactivity, measured by a sensitive bioassay, was identical to CCK-ir levels in the absence of loxiglumide; in the presence of loxiglumide, no circulating CCK-like bioactivity was detectable, indicating complete inhibition of plasma CCK. MCTT was augmented 24% (P less than 0.05). Oral treatment with loxiglumide increased stool weight 72% (P less than 0.01) and fecal fat excretion 186% (P less than 0.001). In conclusion, 1) meal-induced gallbladder contraction and fasting tone are primarily controlled by CCK; 2) the contribution of CCK to the intestinal phase of postprandial pancreatic enzyme secretion is 40-50%; 3) GI motility and absorption are partially controlled by CCK; and 4) postprandial CCK secretion is substantially augmented by loxiglumide via an unknown mechanism.

The effect of the potent specific cholecystokinin (CCK) receptor antagonist loxiglumide on meal-stimulated plasma concentrations of CCK, gastrin, pancreatic polypeptide (PP), neurotensin, glucose-dependent insulinotropic polypeptide (GIP), insulin and C peptide was investigated in a placebo-controlled study in 10 healthy male volunteers. Intravenous infusion of loxiglumide (10 mg kg-1 h-1) significantly augmented integrated incremental IR-CCK levels 7.3-fold after stimulation by a standard breakfast (504 +/- 54 vs 3.665 +/- 365 pmol-1 135 min-1, P less than 0.001), as measured by a specific CCK radioimmunoassay. Basal IR-CCK concentrations were not affected by administration of loxiglumide. Oral treatment with bile acids (2 g ursodeoxycholic acid plus 2 g chenodeoxycholic acid) together with the meal abolished this augmentation, whereas high-dose substitution with pancreatic enzymes (4.2 g pancreatin) reduced elevated IR-CCK levels by only 38%. CCK-like bioactivity, determined by a bioassay using rat pancreatic acini, was not detectable in all samples that contained loxiglumide at plasma concentrations of 100-250 micrograms ml-1. Plasma gastrin concentrations in response to the breakfast were elevated 3.2-fold during loxiglumide infusion and not influenced by substitution with bile acids or pancreatic enzymes. Meal-stimulated integrated incremental plasma PP concentrations were significantly suppressed (55-65% inhibition, P less than 0.01) by loxiglumide. Infusion of the CCK receptor antagonist only slightly increased postprandial peak plasma glucose, insulin and C-peptide levels, whereas GIP and neurotensin levels were not significantly influenced. These findings suggest: (i) CCK secretion is under feedback control by intraduodenal bile acids and to a lesser extent by pancreatic enzymes; (ii) simultaneous extraction of CCK and loxiglumide results in circulating plasma CCK-like bioactivity of zero; (iii) gastrin secretion is feedback controlled via an indirect mechanism probably involving CCK-induced somatostatin secretion; (iv) release of PP is under inhibitory control of CCK; (v) CCK does not play a major role as insulinotropic hormone in the entero-insular axis in humans.

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We characterized the effect of the specific cholecystokinin (CCK) receptor antagonist loxiglumide (CR 1505) on gallbladder contraction, pancreatic enzyme output and plasma CCK concentrations determined by radioimmunoassay and bioassay. Gallbladder emptying and bilirubin output in response to the intraduodenal administration of a mixed liquid meal were completely inhibited by an intravenous infusion of loxiglumide (10 mg/ kg/h). In contrast, meal-stimulated pancreatic enzyme secretion was diminished by only 30–40%. CCK concentrations in response to the test meal were 3-fold higher during infusion of loxiglumide, as determined by radioimmunoassay. In the absence of the antagonist, the bioassay measured CCK plasma levels identical to those determined by radioimmunoassay. In the presence of loxiglumide, CCK-like bioactivity was not detectable, indicating that the plasma concentrations of the CCK receptor antagonist were sufficient to abolish all circulating CCK-like bioactivity. We conclude that fasting volume and meal-induced contraction of the gallbladder are controlled by CCK. Postprandial pancreatic enzyme secretion, however, is mainly mediated by non-CCK-dependent mechanisms. Plasma CCK-like immunoreactivity is increased by loxiglumide, whereas plasma CCK-like bioactivity is zero in the presence of an CCK-receptor antagonist.

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