Splanchnic fluxes of amino acids after duodenal infusion of carbohydrate solutions containing free amino acids or oligopeptides in the non-anaesthetized pig

Abstract

_~~_ _ _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...

Effect of adding sugar beet fibre and wheat bran to a starch diet on the absorption kinetics of glucose, amino-nitrogen and volatile fatty acids in the pig

“…Thus, to study the total absorption of nutrients originating from the enzymatic digestion, the establishment of intestinal balances for a given meal would require blood samplings for 18 h h during the postprandial period. However, according to the variation in the postprandial concentrations of these nutrients the porto-arterial differences generally became low or nil after hour 12 The portal flow rate expressed relative to the animal weight (mL/kg/min) was slightly lower than in previous studies [25,33]. This difference can be explained by the fact that, in the present experiment, the animals were heavier than in the previous ones.…”

“…The main limitation of this method is related to the metabolism in the epithelial cells which can take up a part of the nutrients released in the intestinal lumen (glucose and amino acids: Rerat et al [33]), but also metabolites produced by microbial fermentation [18]. Addi [23].…”

Portal absorption of 14C after ingestion of spiked milk with 14C-phenanthrene, 14C-benzo[a]pyrene or 14C-TCDD in growing pigs

“…14 C meal absorption rate was calculated as: "portal absorption of 14 C / 14 C content in the meal". Blood flow per min and per kg body weight could be estimated thanks many references using growing pigs (Rérat et al, 1987;Simoes Nunes et al, 1989;Rérat et al, 1991;Rérat et al, 1992;Guillot et al, 1993;Guillot et al, 1994;Rérat et al, 1996;Santamaria et al, 1997;Lang et al, 1999;Le Floc'h et al, 1999;Vaugelade et al, 2000).…”

Contribution of erythrocytes and plasma in threonine and lysine transfer across the portal drained viscera and the liver in pigs. Effect of threonine and lysine dietary supply

“…In the case of lysine, the increase in liver uptake helps to limit lysine accumulation in the systemic plasma by favoring lysine catabolism in the liver. In pigs, threonine seem to be less efficiently extracted into the liver than the other essential AA [20]. In a previous study using labelled tracer, we have shown that threonine entry in the liver was low and fairly constant for low and adequat dietary supplies, which corresponds to the experimental situations of experiment 1, but increased sharply with excess supply [12].…”