Is caseinomacropeptide from milk proteins, an inhibitor of gastric secretion?

The aim of this work was to study, in vivo, the effect of the ingestion of not glycosylated caseinomacropeptide (CMP) on gastric secretion. In Experiments #1 and #2, 7 calves fitted with a gastric pouch received either a diet without CMP (C diet) or C diet in which CMP was introduced (equal to and 5 folds that of CMP quantity contained in cow milk, diets CMP1 and CMP5, respectively). In Experiment #3, 2 calves (with gastric pouch) were fed C diet followed by an "iv perfusion" of CMP. In Experiment #4, 25 calves fed either C, CMP1 or CMP5 diets were fitted with a blood catheter for sample collections. The quantities of daily gastric secretions seemed few modified by CMP ingestion but the profile of these secretions was changed along the day. The most important result is that CMP can inhibit gastric secretions (mainly hydrochloric acid) stimulated by the meal, but there was no dose-dependent response. No similar observations were obtained after perfusion of CMP in jugular vein. CMP was not detected in blood. Results obtained in our experiments are not in favor of its significant intestinal absorption. Gastrin, somatostatin and VIP could be implicated in the mechanisms of regulation.

Supplemental sodium butyrate stimulates different gastric cells in weaned pigs.

Sodium butyrate (SB) is used as an acidifier in animal feed. We hypothesized that supplemental SB impacts gastric morphology and function, depending on the period of SB provision. The effect of SB on the oxyntic and pyloric mucosa was studied in 4 groups of 8 pigs, each supplemented with SB either during the suckling period (d 4-28 of age), after weaning (d 29 to 39-40 of age) or both, or never. We assessed the number of parietal cells immunostained for H+/K+-ATPase, gastric endocrine cells immunostained for chromogranin A and somatostatin (SST) in the oxyntic mucosa, and gastrin-secreting cells in the pyloric mucosa. Gastric muscularis and mucosa thickness were measured. Expressions of the H+/K+-ATPase and SST type 2 receptor (SSTR2) genes in the oxyntic mucosa and of the gastrin gene in the pyloric mucosa were evaluated by real-time RT-PCR. SB increased the number of parietal cells per gland regardless of the period of administration (P < 0.05). SB addition after, but not before, weaning increased the number of enteroendocrine and SST-positive cells (P < 0.01) and tended to increase gastrin mRNA (P = 0.09). There was an interaction between the 2 periods of SB treatment for the expression of H/K-ATPase and SSTR2 genes (P < 0.05). Butyrate intake after weaning increased gastric mucosa thickness (P < 0.05) but not muscularis. SB used orally at a low dose affected gastric morphology and function, presumably in relationship with its action on mucosal maturation and differentiation.

Differential activation of adenylate cyclase by secretin and VIP receptors in the calf pancreas.

OBJECTIVE: Secretin is a key regulator of pancreatic secretion, but the molecular basis of its action is not well understood, especially in the calf pancreas. Our study investigated the expression and functional competence of secretin receptors (SEC-R) in calf pancreatic membranes. METHODS: We used reverse transcriptase-polymerase chain reaction, sequencing, and Northern blot to assess the expression of the SEC-R gene. The functional characterization of SEC-R was accomplished using adenylate cyclase (AC) assay. RESULTS: We successfully amplified, by reverse transcriptase-polymerase chain reaction, a fragment of the SEC-R gene from 119-day-old calf pancreas. This sequence shows higher homology with SEC-R than with vasoactive intestinal polypeptide (VIP)-1 and VIP-2 receptors from other species. Northern blot analysis detected a 1.8-kb transcript. Accordingly, secretin stimulates AC activity in calf pancreatic membranes isolated from 28- and 119-day-old animals with a potency (Ka) of 1.9 to 2.7 nmol/L. Maximal AC stimulation induced by secretin represented a 3- to 4-fold increase of basal activity. AC activation by secretin was inhibited by the 2 SEC-R antagonists, [psi4,5] secretin (l micromol/L) and [5-27] secretin (10 micromol/L). Interestingly, [psi4,5] secretin was ineffective against VIP-induced AC stimulation. CONCLUSION: Our data indicate that secretin exerts a direct action on pancreatic secretion through specific SEC-R coupled to the AC system. Calf pancreatic SEC-Rs are coexpressed with VIP-2 receptors that we previously identified by ligand binding and cross-linking experiments.

Bovine pancreatic secretion in the first week of life: potential involvement of intestinal CCK receptors.

The aim of this study was to evaluate pancreatic juice secretion of calves in the first postnatal days, and determine a potential involvement of cholecystokinin (CCK) and intestinal CCK receptor in its regulation. Nine neonatal Friesian calves (five controls and four treated intraduodenally with FK480, a CCK-A receptor antagonist) were surgically fitted with a pancreatic duct catheter and a duodenal cannula before the first colostrum feeding. Collections of pancreatic juice and duodenal luminal pressure recordings were started early after recovery from anaesthesia and continued for 6 days. From day 2 or 3 of life, periodic fluctuations in pancreatic secretions were observed in concert with duodenal myoelectric motor complex (MMC) and variations in plasma pancreatic polypeptide (PP) concentrations. Intraduodenal administration of FK480 reduced pancreatic juice secretion while intravenous infusion of CCK had no effect. Immunocytochemistry indicated an association of mucosal CCK-A and -B receptors with neural components of the small intestine. In conclusion, periodic activity of the exocrine pancreas exists in neonatal calves soon after birth and local neural intestinal CCK-A receptors could be partly responsible for the modulation of neonatal calf pancreatic secretion.