Uptake of labelled phenylalanine into different blood fractions in the portal vein and cranial mesenteric vein of lambs

Neutze, S. A.; Gooden, J. M.; Oddy, V. H.

doi:10.1017/s0021859600075602

Cited by 5 publications

(5 citation statements)

References 22 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Whatever the diet, PAA net release across the MDV was not significantly different from PDV net release; and, as observed in sheep fed fresh forage (13) , the small intestine was the main contributor to PAA net release across the PDV (56 %). Peptide contribution to MDV net release of essential AA was only 7-8 %, with this contribution being slightly lower than previously reported in sheep (14 %) (13) , and in lambs (up to 20 %) (21) . Urea transfer to the small intestine, and its contribution to urea net uptake across the PDV, decreased with pea extrusion, probably as a consequence of the decrease in blood urea concentration.…”

Section: Nitrogen Transactions Across the Mesenteric-drained Visceracontrasting

confidence: 62%

Partitioning of nutrient net fluxes across the portal-drained viscera in sheep fed twice daily: effect of dietary protein degradability

et al. 2009

View full text Add to dashboard Cite

Extrusion is used to decrease leguminous seed protein degradability in the rumen in order to shift part of the dietary protein digestion towards the small intestine. The effect of such displacement of digestion site on the partitioning of nutrient net fluxes across the gastrointestinal tract was studied using four sheep fitted with catheters and blood-flow probes, allowing measurements across the rumen, the mesenteric-drained viscera (MDV) and the portal-drained viscera (PDV). Two diets containing 34 % of pea seeds were tested in a crossover design. They differed only according to pea treatment: raw pea (RP) or extruded pea (EP) diet. Rumen undegradable protein (RUP) accounted for 23 and 40 % of dietary crude protein for RP and EP diets, respectively. Across the rumen wall, ammonia net flux was lower with EP diet, whereas urea net flux was not different. Across the MDV, free amino acid (FAA) net flux was greater with EP diet, whereas peptide amino acid net flux was not different, accounting for 7 % of the non-protein amino acid net release. From RP to EP diet, PDV net flux of ammonia decreased by 23 %, whereas FAA net release increased by 21 %. The difference in dietary RUP did not affect the PDV net flux of SCFA, 3-hydroxybutyrate, lactate and glucose. In conclusion, the partial shift in pea protein digestion from the rumen to the small intestine did not affect the portal net balance of N, but decreased N loss from the rumen, and increased amino acid intestinal absorption and portal delivery.Amino acids: Peptides: Short-chain fatty acids: Portal-drained viscera Proteins consumed by ruminants are largely degraded in the rumen, up to ammonia production, in order to provide N required for microbial growth. Consequently, the outflow from the rumen of synthesized microbial protein ensures the largest contribution to amino acids (AA) entering the small intestine. Nevertheless some dietary proteins, more resistant, can escape ruminal degradation and complement the microbial AA source quantitatively and qualitatively to meet maintenance and production needs (1) . Conversely, dietary protein readily degraded in the rumen often leads to N wastage through excessive ammonia absorption from the rumen. Processing has thus been developed in order to decrease rumen degradability of feedstuff, and increase the AA delivery to the intestine. However, an increased flow of protein-N to the duodenum does not necessarily imply an increased availability of AA for anabolic purposes due to the intense metabolic activity of the splanchnic bed. More specifically, the digestive tract is one of the most important AA consumers within the body and participates to about 30 % of the whole-body protein synthesis (2) . This metabolism greatly impacts on the quantitative and qualitative net release of AA in the portal vein (3) . Yet, even if the digestive tract is metabolically very active and is withdrawing important quantities of AA, increasing dietary protein supply usually results in a greater portal absorption of AA, as far as the energy supp...

show abstract

Section: Nitrogen Transactions Across the Mesenteric-drained Visceracontrasting

confidence: 62%

Partitioning of nutrient net fluxes across the portal-drained viscera in sheep fed twice daily: effect of dietary protein degradability

et al. 2009

View full text Add to dashboard Cite

show abstract

“…Our preliminary study on peptide determination showed that the estimation of plasma PAA is largely affected by the sample preparation. The chemical deproteinization with SSA is known to leave small quantities of protein in the supernatant (Hubbard et al, 1988;Neutze et al, 1996), whatever the final concen- tration in SSA. That probably explains the large concentration of AA (7,160 M in the artery) attributed to plasma peptide by McCormick and Webb (1982).…”

Section: Discussionmentioning

confidence: 99%

“…erable contribution (65 to 85%) of PAA to PDV net flux of AA (FAA + PAA) has been observed in steers (Webb et al, 1992;Koeln et al, 1993;Seal and Parker, 1996). In sheep, large (90%; Webb et al, 1992), low (20% for Phe; Neutze et al, 1996), or nonsignificant (Backwell et al, 1997) contributions of PAA were reported. Furthermore, it seemed that PAA release in the portal vein of steers mainly originates from the non-mesenteric area (Webb et al, 1992;Seal and Parker, 1996).…”

Section: Introductionmentioning

confidence: 96%

Free and peptide amino acid net flux across the rumen and the mesenteric- and portal-drained viscera of sheep.

Rémond

Bernard

Poncet

2000

Journal of Animal Science

View full text Add to dashboard Cite

This experiment was conducted to determine the significance of the peptide amino acid (PAA) contribution to amino acid (AA) net flux in the portal vein and to evaluate the capacity for peptide absorption in the different segments of the gastrointestinal tract of ruminants. Four sheep (64+/-3 kg BW) were fitted with catheters and blood flow probes, allowing AA net flux measurements across the portal- (PDV) and mesenteric (MDV)-drained viscera and the rumen. Sheep were fed at maintenance a diet containing hay and extruded peas (70:30). Peptide absorption was investigated by a dose infusion of a mixture of peptides (casein hydrolysate, Pro-Phe, beta-Ala-His, Gly-Gly) into the rumen. Control and postinjection net fluxes of plasma free amino acids (FAA) and PAA were determined. The concentration of plasma PAA was determined by quantification of amino acids before and after acid hydrolysis of samples first submitted to chemical deproteinization and ultrafiltration (3-kDa cut-off filter). During the control period a significant net release (12 mmol/h) of PAA was observed across the PDV, which accounted for 35% of the sum of FAA and PAA net fluxes. This PDV flux of PAA mainly resulted from a MDV release of PAA (15 mmol/h). The net flux of total PAA across the ruminal wall was not significantly different from zero, but uptake of peptide Ile and release of peptide Gly were observed. The injection into the rumen of the peptide mixture increased the net release of peptide essential AA (EAA) across the MDV (P < .05) and the PDV (P < .10), and of peptide Pro and Phe across the non-MDV (P < .10). Peptide Ile uptake by the rumen tissues was decreased by the injection (P < .05). Significant increases in peptide Pro and Gly arterial concentrations were observed (P < .05). The 3-Ala-His and Gly-Gly arterial concentrations and net fluxes across the PDV were not affected by their injections into the rumen. This study showed that PAA may contribute significantly to AA flux across the PDV of sheep, and that part of this flux can probably be attributed to peptide absorption from the gut lumen. When high concentrations of peptides are generated in the rumen the possibility of peptide absorption before the jejunum has to be considered.

show abstract

“…At any rate, net flux of free amino acids appears to be low compared with peptide-bound amino acids in ruminants (Koeln et al, 1993;Webb et al, 1993;Han et al, 2001). Based on evidence that chemical deproteinization overestimates the peptide amino acid concentration in plasma (Bernard and Rémond, 1996;Backwell et al, 1997), it has been suggested that the high flux of peptides might be due to the procedure of sample deproteinization (Neutze et al, 1996;Backwell et al, 1997). Methods for measuring peptides have generally relied on the difference method, where amino acid analysis of deproteinized samples before and after acid hydrolysis has occurred, with the difference being attributed to peptides.…”

Section: Net Portal-drained Visceral Flux Of Peptidesmentioning

confidence: 99%

Absorption of amino acids and peptides.

Krehbiel¹,

Matthews²,

D’Mello³

2003

Amino Acids in Animal Nutrition

View full text Add to dashboard Cite

Gastric and luminal hydrolysis Na ϩ Fig. 3.1. The current model for the role of peptide uptake in protein assimilation, as adapted from Ganapathy et al. (1994). The relative contribution of peptide (di-, tri-) versus free amino acid (AA) to total protein assimilation through hydrolytic and transport events is indicated by the relative thickness of the lines. After hydrolysis by gastric proteases and luminal peptidases, oligopeptides are hydrolysed to small peptides and free amino acids by apical membrane-bound (1) peptidases. Peptides are absorbed across brush border membrane by PepT1 (2). Whereas a small proportion of absorbed peptides are then absorbed intact across the basolateral membrane by a H +-independent transport activity (3), the majority are hydrolysed by intracellular peptidases (4). The resulting free AA, plus those absorbed across the apical membrane by a complement of Na +-dependent and-independent amino acid transporters (5) are then transported across the basolateral membrane by a complement of Na +-independent and amino acid exchanger transport proteins (6). The extracellular-intracellular H + gradient that drives PepT1 activity, is re-established by the combined function of the apical Na + /H + exchanger (7) and the basolateral Na + /K + ATPase (8), which re-establishes the extracellular-intracellular Na + gradients diminished by both Na + /H + exchanger and Na +-coupled free amino acid transport. The contribution to total protein assimilation by free AA uptake from the lumen is represented by a composite transporter model (7), representing AA transport by Na +-coupled, AA counterexchange, and/or facilitated transport proteins. The transepithelial passage of intact proteins is also indicated (dashed line). The mechanisms responsible for this relatively minor, but immunologically important process, have been reviewed by Gardner (1994).

show abstract

Uptake of labelled phenylalanine into different blood fractions in the portal vein and cranial mesenteric vein of lambs

Cited by 5 publications

References 22 publications

Partitioning of nutrient net fluxes across the portal-drained viscera in sheep fed twice daily: effect of dietary protein degradability

Partitioning of nutrient net fluxes across the portal-drained viscera in sheep fed twice daily: effect of dietary protein degradability

Free and peptide amino acid net flux across the rumen and the mesenteric- and portal-drained viscera of sheep.

Absorption of amino acids and peptides.

Contact Info

Product

Resources

About