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.
Based on in vitro findings with mouse mast cells and in vivo findings in mice, we report that dexamethasone or cyclosporin A can have at least three actions which interfere with the pathogenesis IgE-, mast-cell-, and cytokine-dependent inflammatory reactions: suppression of the IgE-dependent increase in tumor necrosis factor (TNF)-α mRN A by mast cells, inhibition of the IgE-dependent production of TNF-α protein by mast cells, and diminution of the responsiveness of target cells to TNF-α. Our findings in mice raise the possibility that similar actions of these agents in humans may account for some of the clinical efficacy of corticosteroids and cyclosporin A in allergic diseases.
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