Effect of bombesin at low doses on the secretion of the exocrine pancreas and on plasma gastrin concentration in the conscious pig.

We investigated the role of low-doses of bombesin in the regulation of exocrine secretion in the pancreas of the conscious pig. In ten growing castrated male Large White pigs, bombesin was infused intravenously for 1 h at doses of 0 to 500 pmol/kg/h under a stimulation of secretin (36 pmol/kg/h). In six pigs, bombesin (50 pmol/kg/h) was administered alone for 2 h and its effect on pancreatic secretion was compared to that of an infusion of secretin. The pancreatic juice and the blood were collected at 15-min intervals for use in assays of protein in the juice and gastrin in the plasma. When bombesin was infused alone or in combination with secretin, the volume secreted was not altered. The protein output was not altered by secretin, but was increased by the infusion of bombesin, in a dose-dependent manner, reaching a plateau at 250 pmol/kg/h. The plasma gastrin levels were increased by bombesin, starting with the 50 pmol/kg/h dose. This effect was maximal at a dose of 100 pmol/kg/h. The levels remained below those measured after a standard meal, demonstrating that the effect of bombesin on the studied parameters is of physiological significance.

Physiological effects of a pea protein isolate in gnotobiotic rats: comparison with a soybean isolate and meat.

Pea proteins have been considered for the introduction into the human diet only recently. This protein source was tested on nutritional and digestive parameters in heteroxenic male Fischer rats inoculated with a human faecal microflora from a methane producer. Compared to soybean proteins, pea proteins have similar effects on the rat's endogenous and bacterial digestive patterns. Compared to the pea proteins, a diet containing a standard meat meal enhanced the pH and the production of ammonia, while a lyophilized beef meat enhanced that of urea. The diet containing the standard meat decreases short-chain fatty acids and modifies the ratio of caecal short-chain fatty acids. Both animal diets decreased the specific activities of pancreatic proteases such as chymotrypsin (EC 3.4.21.1), trypsin (EC 3.4.21.4), and carboxypeptidase A (EC 3.4.17.1) when compared to the diet containing the pea isolate. In conclusion, the whole composition of the diet, more than the origin of the dietary protein, influences the rat's digestive pattern.

Influence of caecal microflora and of two dietary protein levels on the adaptation of the exocrine pancreas: comparative study in germ-free and conventional rats.

Dietary proteins are degraded by both endogenous enzymes and the caecal microflora. In conventional rats the enzyme content of the pancreas depends on the amount of dietary protein. The influence of the caecal microflora on this process is unknown. We report here the effect of the caecal microflora on pancreatic enzymes (proteases, amylase (EC 3.2.1.1), lipase (EC 3.1.1.3)) and on colonic metabolites (NH3, urea, short-chain fatty acids). Germ-free and conventional male Fischer rats were fed for 3 weeks with a diet containing 220 or 450 g protein/kg provided as a mixture of fish concentrate and soyabean isolate. The excretion of NH3 and the pH were specifically increased by the high-protein diet in the germ-free rats. The higher production of isobutyrate, valerate and isovalerate in conventional rats fed on the high-protein diet reflected a high bacterial proteolytic activity since these short-chain fatty acids are specific indicators of this activity. The microflora hydrolysed urea to NH3 and maintained the pH at neutrality whatever the amount of protein in the diet since there were changes in germ-free rats but not in conventional ones. In germ-free rats, amylase, trypsin (EC 3.4.21.4), elastase (EC 3.4.21.36) and carboxypeptidase A (EC 3.4.17.1) specific activities were significantly lower than in conventional rats. The adaptation of the pancreas to the 450 g protein/kg diet was not impaired by the bacterial status except for the specific activity of chymotrypsin (EC 3.4.21.1) which was more increased by this diet in germ-free than in conventional rats. Moreover, the specific activity of lipase increased only in conventional rats fed on the 450 g protein/kg diet. In conclusion, we observed a relationship between the enzyme content of the pancreas and the presence or absence of the caecal microflora suggesting that bacterial fermentation influences pancreatic function.

Early adaptation of pancreas to a protein-enriched diet: role of cholecystokinin and gastrin-releasing peptide.

Feeding rats a diet containing high levels of protein (as casein) increases the secretion and biosynthesis of pancreatic serine proteases. Cholecystokinin (CCK) presumably plays a role in this process although other GI peptides such as the gastrin-releasing peptide (GRP) may be involved. In this article, we describe the kinetics of pancreatic adaptation to a diet containing 45% protein as soybean and fish. Then we report the effect of treatment with either a cholecystokinin-receptor antagonist (MK-329) or a gastrin-releasing peptide-receptor antagonist ([D-F5 Phe6, D-Ala11]-Bn(6-13)OMe, or BIM 26226) on pancreatic adaptation to this diet. Prior to experiments, adult male Fischer rats received a diet containing 22% protein for 1 week. In the first experiment, 48 rats were fed a diet containing 45% protein; they were killed after 0-7 days. In the second experiment, 53 rats were fed the 22- or 45%-protein diet and received three daily injections of either the vehicle alone, MK-329, or BIM 26226 for 7 days before they were killed. When the protein-rich diet was fed for 0-7 days, amylase, in vitro biosynthesis, and mRNA levels were gradually decreased while serine protease biosynthesis was increased, reflecting the general enhancement of chymotrypsinogen, trypsinogen, and elastase mRNA levels. For all these parameters, adaptation leveled off after a 5-day feeding. When the protein diets were fed for 7 days, MK-329 significantly inhibited the adaptation of trypsin (specific activity and mRNA) and elastase (mRNAs) to the 45%-protein diet. BIM 26226 had no effect on pancreatic adaptation to the protein-rich diet.(ABSTRACT TRUNCATED AT 250 WORDS)

Influence of diet composition on intestinal volatile fatty acid and nutrient absorption in unanesthetized pigs.

Two experiments were conducted to study the effect of the amount and nature of fiber and carbohydrates on nutrient and VFA absorption. Five Large White pigs in each crossover experiment were accustomed to a semisynthetic 14% protein diet containing 6 (LC) or 16% (HC) pure cellulose (Exp. 1) or 22% alfalfa meal (6.3% cellulose, HA) and 22% lactose and 6% pure cellulose (HL; Exp. 2). Each animal was then fitted with catheters in the portal vein and carotid artery and with a flow probe around the portal vein. Eight days after surgery, the absorption of reducing sugars (RS) and amino-N was studied for 12 h and that of VFA for 24 h after intake of a single 800-g meal. The alternate diet was then given for 7 to 10 d and a second series of samplings was performed within the same conditions. In the first experiment, added dietary cellulose decreased efficiency of absorption of RS (LC: 90.4 +/- 7.0%; HC: 81.6 +/- 3.6%) and amino-N (LC: 95.3 +/- 9.1%; HC: 70.3 +/- 2.8%; P less than .05). Daily absorption (24 h) of VFA tended to be larger when the cellulose level rose (LC: 1,184 +/- 85 mmol; HC: 1,429 +/- 216 mmol, NS) and increased (P less than .05) with the length of adaptation (21 to 28 d) to the diet, regardless of cellulose level. In the second experiment, after intake of the alfalfa diet, absorption of RS was high (97.8%), whereas absorption of amino-N (74.3%) and VFA (880 +/- 87 mmol/24 h) were low. Intake of lactose reduced absorption of RS (85.2%), did not alter absorption of N (75.9%) and increased absorption of VFA (1,181 +/- 218 mmol/24 h). Thus, the energy efficiency of the diet was lowered (P less than .05) when cellulose was added to the diet but not when alfalfa meal or lactose were added.

Influence of meal frequency on postprandial variations in the production and absorption of volatile fatty acids in the digestive tract of conscious pigs.

Five Large White pigs of 62.2 +/- 1.4 kg mean body weight were fitted with permanent catheters in the portal vein and carotid artery and with an electromagnetic flow probe around the portal vein to study the absorption of volatile fatty acids (VFA) by measuring the concentration of these metabolites in hourly blood samples, and by determining the portal blood flow rate for a period of 12 h after intake of a single 800-g meal (6% crude fiber) preceded by 12 or 24 h of fasting. The portal concentration of VFA mixture always highly exceeded the arterial concentration. The arterial concentrations of propionic, butyric, valeric and isovaleric acids were nearly null, accounting for an almost complete uptake of these VFA by the liver. Acetic acid also was taken up, but to a lesser extent. Total VFA absorption during 12 h was 64% higher (P less than .05) after 12 h (1,160 +/- 100 mmol/12 h) than after 24 h of preprandial fasting (740 +/- 83 mmol/12 h). It increased after the meal (P less than .05) from 82.3 +/- 7.8 mmol/h between the first and fourth hour to 107.8 +/- 7.5 mmol/h between the fifth and tenth hour when the preprandial fasting lasted 12 h; a nonsignificant increase also was found when fasting prior to the meal lasted 24 h. The composition of the VFA mixture was not modified by the length of preprandial fasting. With this type of diet there was a large predominance of acetic acid (52%) followed by propionic and butyric acids (36 and 8.5%, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

[Effect of the nature of carbohydrates in pig diets on the intestinal absorption of volatile fatty acids]. / Influence de la nature des glucides présents dans le régime du porc sur l'absorption intestinale des acides gras volatils.

The appearance of nutrients (amino nitrogen and reducing sugars) and microbial metabolites (volatile fatty acids, VFA) was measured quantitatively in five pigs. After ingestion of a semi-synthetic diet (RFL) containing 22% lucerne meal (6% crude fibre), the absorption of reducing sugars (RS) in the small intestine was high (97.8%) and that of VFA low (880 +/- mmoles/24 hrs.). Ingestion of a semi-synthetic diet (RLa) containing 22% lactose and 6% purified cellulose led to lower absorption of RS (85.2%) and a higher absorption of VFA (1,180 +/- mmoles/24 hrs).

[Influence of purified cellulose level in the diet of pigs on intestinal absorption of volatile fatty acids]. / Influence du taux de cellulose purifiée dans le régime du porc sur l'absorption intestinale des acides gras volatils.

Nutrient and volatile fatty acid (VFA) absorption to portal blood was measured twice at 7 days interval in five pigs fed a semi-synthetic diet containing 6 (R6) or 16% (R16) purified cellulose for 21 or 7 days. The daily absorption (24 hrs.) of VFA in the large intestine which was larger (NS) when the cellulose level rose, increased significantly (P less than 0.05) with increasing length of adaptation (21 to 28 d.) to the diet whatever the cellulose level. The supplementary daily supply of energy in the form of VFA after increase of the cellulose level did not compensate for the corresponding deficit of absorption of reducing sugars and crude protein in the small intestine.

[Measurement of the appearance of volatile fatty acids in the portal vein during digestion in conscious pigs]. / Mesure de l'apparition dans la veine porte des acides gras volatils formés au cours de la digestion chez le Porc éveillé.

A method used to measure the nutrient exchanges between the intestinal lumen and the portal blood was applied to 3 pigs receiving 800 g of a diet containing 6% of cellulose. During a postprandial period of 24 hrs., the mixture of volatile fatty acids (90 mM/h) appearing in the portal vein was composed of acetic acid (57%), propionic acid (30%), butyric acid (9%), isovaleric (2.5%) and valeric acid (1.5%). The composition of this mixture differed from that of the colic contents because of its acetic acid enrichment at the expense of butyric acid. The resulting energy supply to the animal represented about 600 to 700 kcal/24 hrs.