_~~_ _ _Seven non-anaesthetized pigs (mean body-weight 64.6 kg) were used to study the intestinal absorption and hepatic metabolism of glucose and amino acids (AA) using carbohydrate solutions (maltose dextrin; 440 g/2 I), containing 110 g of either an enzymic milk-protein hydrolysate (PEP) with a large percentage of small peptides (about 50% with less than five AA residues) and very few free AA (8%) or a mixture of free AA (AAL) with an identical pattern, infused intraduodenally. Each pig was previously fitted under anaesthesia with electromagnetic flow probes around the portal vein and the hepatic artery, and with permanent catheters in the portal vein, carotid artery, one hepatic vein and the duodenum. Each solution was infused for 1 h after a fasting period (18 h) and each pig received both solutions at 8 d intervals. The observation period lasted 8 h. For most AA (his, lys, phe, thr, arg, tyr, pro) the absorption rate after infusion of P E P was significantly higher than after that of AAL during the 1st hour, but the differences quickly disappeared. After 8 h, the only differences concerned his and tyr (PEP > AAL) and met, glu and asp (AAL > PEP). There was a large uptake of blood AA by gut-wall cells, higher after AAL infusion than after P E P infusion, particularly for branched-chain AA (BCAA). The absorption of ammonianitrogen after both infusions was equivalent to two-thirds of urea-N passing from blood to intestinal tissues and lumen. Glucose absorbed within 8 h represented only 76% (PEP) or 69% (AAL) of the infused amounts. The cumulative hepatic total AA (TAA) uptake increased from 13 to 27% of the infused amounts between the 1st and the 8th hour after P E P infusion, and from 8 to 31 YO after AAL infusion. Most essential AA were largely taken up by the liver, with the exception of met (PEP) and thr and of BCAA, which were poorly retained for both solutions; there was a high uptake of ala and gly, and a release of asp, glu, and gln. Urea-N released by the liver within 8 h was equivalent to 23-25% absorbed amino-N and to around 1 5 times ammonia-N taken up by the liver within 8 h. Glucose was highly taken up by the liver during the first hours then released, the total uptake within 8 h representing about half the absorbed amount. There was a lactate release tending to he higher after P E P than after AAL infusion and a liver pyruvate release identical for both solutions. From calculations of net noncatabolic metabolism in the liver the possible synthesis of liver proteins within 8 h may be estimated at 35 g for both solutions. The cumulative peripheral TAA uptake increased from 12 to 27 % of the infused amounts between the 1st and 8th hour after P E P and from 9 to 11 % after AAL infusion. At 8 h after the infusion the larger uptake concerned BCAA, arg, glu and asp and there was a marked release of gln, gly and ala for both solutions; the peripheral balance was zero for met (PEP) or characterized by a release of phe and thr (AAL). Thus, protein synthesis seemed only to be possible with the aid of plas...

Summary. Regulation of pancreatic secretion in the pig by negative feedback and plasma gastrointestinal hormones. Introduction.

The fasting hypoglycemia (1.78 +/- 0.29 mmol/l) which develops in 48-h-old pigs is partially reversed (3.85 +/- 0.55 mmol/l) after gastric administration of long-chain triglycerides (LCT). The increase in blood glucose induced by LCT feeding was not secondary to a decreased glucose utilization because glucose disappearance rate increased in LCT-fed piglets but resulted from a twofold increase in glucose appearance. By using the crossover-plot technique, the stimulation of hepatic gluconeogenesis induced by LCT feeding has been localized at 1) the level of pyruvate carboxylase owing to the twofold increase in hepatic acetyl-CoA concentration and 2) the level of glyceraldehyde-3-phosphate dehydrogenase secondary to the increase in reducing equivalents (NADH), which displaces this equilibrium reaction in the direction of gluconeogenesis. As blood lactate, pyruvate, and alanine concentrations increased after LCT feeding, the possible effects of LCT on pyruvate dehydrogenase in peripheral tissues are discussed. These data demonstrate that fatty acids stimulate hepatic gluconeogenesis in 48-h-old fasting piglets and underline the role of fat provision in the regulation of glucose homeostasis during the neonatal period in the pig.

Summary.The digestive physiology of the germ-free animal has a number of characteristics (cecal hypertrophy, slower small intestine cell renewal, slower gastric emptying and intestinal transit) which distinguish it from that of the conventional animal. If the germ-free model is to be used to determine the role of gastrointestinal microflora in the nutrition of the conventional animal, it is essential to complete the study of these characteristics by data on digestive enzymes in the germ-free. The present paper analyzes these data.There In general, the germ-free animal has some characteristics which should permit better utilization of the diet ingested. Measurements of apparent digestibility do not confirm this hypothesis since results obtained in germ-free and conventional animals of the same species are contradictory.The germ-free animal is certainly a very useful tool for studying the role of gastrointestinal microflora in the nutrition of its host. The large intestine contains the largest bacterial population (1 to 3.10 10 bacteria/g fresh contents) and the greatest number of microbial species in the gut (Ducluzeau and Raibaud, 1975 ;Schaedler, 1973). In some cases, bacteria may efficiently intervene in the digestive utilization of the diet ingested by the animal (R6rat, 1978).However, a number of experiments in the germ-free animal have shown that it cannot be considered simply as a conventional animal, deprived of gastrointestinal microflora, since certain characteristics of its digestive physiology distinguish it from the conventional animal (see reviews by Gordon et al.,1966 ;Combe et al., 1976). A knowledge of these characteristics is essential when determining the part due to bacteria in the digestion of an ingested diet.The germ-free state in rodents and lagormorphs leads to a substantial increase in cecal sac contents and size (Glimstedt, 1936 ;Wostmann and Bruckner-Kardoss, 1959 ;Wostmann, Bruckner-Kardoss and Knight, 1968 ;Pleasants, 1959 (Guenet et al., 1970). In the chicken, the rate of epithelial cell migration is lower in the germ-free than in the conventional state, but the relative differences are greater in the lower than in the upper intestine (Rolls, Turvey and Coates, 1978).Gastric emptying and small intestinal transit of the ingested food were found to be slower in the germ-free than in the conventional state. Six hours after a labelled test-meal, the cecum of the germ-free mouse retained a greater percentage of radioactivity than the cecum of the conventional animal, and the passage of the marker into the feces was slower (Abrams and Bishop, 1967). Gastrointestinal transit was also slower in the germ-free than in the conventional rat (Sacquet, Garnier and Raibaud, 1970 ;Riottot et al., 1980), and tended to be longer in germ-free rats fed irradiated diets than in those fed autoclaved diets (Riottot et al.,1980). The aim of the present review is to complete our knowledge of the characteristics of germ-free animal digestive physiology by analyzing data on digestive enzymes. These enzymes (p...

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