Amino acid use by the gastrointestinal tract of sheep given lucerne forage

J C MacRae, L A Bruce, David Stanley Brown, Alexander Graham Calder

    Research output: Contribution to journalArticle

    60 Citations (Scopus)

    Abstract

    Essential amino acid (EAA) utilization by gastrointestinal tract (GIT) tissues has been investigated in sheep given 800 and 1,200 g/day lucerne pellets. Animals prepared with indwelling catheters into the aorta and the portal drained viscera plus cannulas into the small intestine were infused with mixed U-C-13-labeled amino acid or [1-C-13]leucine tracers into the jugular vein or directly into the small intestine. GIT sequestration of EAA from arterial and luminal AA pools was determined from tracer and tracee arterioportal concentration differences at both levels of intake. Proportional tracer C-13-labeled EAA extraction of the arterial supply, on first pass across the GIT during jugular infusion, ranged from 0.063 for histidine to 0.126 for leucine. Recovery of intestinally infused tracer C-13-EAA at the portal vein ranged from 0.61 for histidine to 0.83 for valine. These data were independent of intake. Calculated rates of tracee sequestration by GIT tissues represented 0.45-0.65 of whole body EAA flux, except for histidine, for which the values were much lower (0.25-0.32). With the exception of phenylalanine, more than 0.8 of the EAA used by the GIT was extracted from circulating blood, thus calling into question the theory that GIT tissues make preferential use of EAA during absorptive metabolism, restricting supply to peripheral tissues such as skeletal muscle (growth) or mammary glands (lactation). Instead the GIT seems to compete very successfully with these tissues for circulating blood EAA.

    Original languageEnglish
    Number of pages8
    JournalAmerican journal of physiology. Gastrointestinal and liver physiology
    Volume36
    Issue number6
    Publication statusPublished - Dec 1997

    Keywords

    • stable isotopes
    • PROTEIN-SYNTHESIS
    • GROWING LAMBS
    • WHOLE-BODY
    • EFFICIENCY
    • METABOLISM
    • ABSORPTION
    • RUMINANTS
    • NITROGEN
    • TISSUES
    • CONSEQUENCES

    Cite this

    Amino acid use by the gastrointestinal tract of sheep given lucerne forage. / MacRae, J C ; Bruce, L A ; Brown, David Stanley; Calder, Alexander Graham.

    In: American journal of physiology. Gastrointestinal and liver physiology , Vol. 36, No. 6, 12.1997.

    Research output: Contribution to journalArticle

    MacRae, J C ; Bruce, L A ; Brown, David Stanley ; Calder, Alexander Graham. / Amino acid use by the gastrointestinal tract of sheep given lucerne forage. In: American journal of physiology. Gastrointestinal and liver physiology . 1997 ; Vol. 36, No. 6.
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    abstract = "Essential amino acid (EAA) utilization by gastrointestinal tract (GIT) tissues has been investigated in sheep given 800 and 1,200 g/day lucerne pellets. Animals prepared with indwelling catheters into the aorta and the portal drained viscera plus cannulas into the small intestine were infused with mixed U-C-13-labeled amino acid or [1-C-13]leucine tracers into the jugular vein or directly into the small intestine. GIT sequestration of EAA from arterial and luminal AA pools was determined from tracer and tracee arterioportal concentration differences at both levels of intake. Proportional tracer C-13-labeled EAA extraction of the arterial supply, on first pass across the GIT during jugular infusion, ranged from 0.063 for histidine to 0.126 for leucine. Recovery of intestinally infused tracer C-13-EAA at the portal vein ranged from 0.61 for histidine to 0.83 for valine. These data were independent of intake. Calculated rates of tracee sequestration by GIT tissues represented 0.45-0.65 of whole body EAA flux, except for histidine, for which the values were much lower (0.25-0.32). With the exception of phenylalanine, more than 0.8 of the EAA used by the GIT was extracted from circulating blood, thus calling into question the theory that GIT tissues make preferential use of EAA during absorptive metabolism, restricting supply to peripheral tissues such as skeletal muscle (growth) or mammary glands (lactation). Instead the GIT seems to compete very successfully with these tissues for circulating blood EAA.",
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    T1 - Amino acid use by the gastrointestinal tract of sheep given lucerne forage

    AU - MacRae, J C

    AU - Bruce, L A

    AU - Brown, David Stanley

    AU - Calder, Alexander Graham

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    N2 - Essential amino acid (EAA) utilization by gastrointestinal tract (GIT) tissues has been investigated in sheep given 800 and 1,200 g/day lucerne pellets. Animals prepared with indwelling catheters into the aorta and the portal drained viscera plus cannulas into the small intestine were infused with mixed U-C-13-labeled amino acid or [1-C-13]leucine tracers into the jugular vein or directly into the small intestine. GIT sequestration of EAA from arterial and luminal AA pools was determined from tracer and tracee arterioportal concentration differences at both levels of intake. Proportional tracer C-13-labeled EAA extraction of the arterial supply, on first pass across the GIT during jugular infusion, ranged from 0.063 for histidine to 0.126 for leucine. Recovery of intestinally infused tracer C-13-EAA at the portal vein ranged from 0.61 for histidine to 0.83 for valine. These data were independent of intake. Calculated rates of tracee sequestration by GIT tissues represented 0.45-0.65 of whole body EAA flux, except for histidine, for which the values were much lower (0.25-0.32). With the exception of phenylalanine, more than 0.8 of the EAA used by the GIT was extracted from circulating blood, thus calling into question the theory that GIT tissues make preferential use of EAA during absorptive metabolism, restricting supply to peripheral tissues such as skeletal muscle (growth) or mammary glands (lactation). Instead the GIT seems to compete very successfully with these tissues for circulating blood EAA.

    AB - Essential amino acid (EAA) utilization by gastrointestinal tract (GIT) tissues has been investigated in sheep given 800 and 1,200 g/day lucerne pellets. Animals prepared with indwelling catheters into the aorta and the portal drained viscera plus cannulas into the small intestine were infused with mixed U-C-13-labeled amino acid or [1-C-13]leucine tracers into the jugular vein or directly into the small intestine. GIT sequestration of EAA from arterial and luminal AA pools was determined from tracer and tracee arterioportal concentration differences at both levels of intake. Proportional tracer C-13-labeled EAA extraction of the arterial supply, on first pass across the GIT during jugular infusion, ranged from 0.063 for histidine to 0.126 for leucine. Recovery of intestinally infused tracer C-13-EAA at the portal vein ranged from 0.61 for histidine to 0.83 for valine. These data were independent of intake. Calculated rates of tracee sequestration by GIT tissues represented 0.45-0.65 of whole body EAA flux, except for histidine, for which the values were much lower (0.25-0.32). With the exception of phenylalanine, more than 0.8 of the EAA used by the GIT was extracted from circulating blood, thus calling into question the theory that GIT tissues make preferential use of EAA during absorptive metabolism, restricting supply to peripheral tissues such as skeletal muscle (growth) or mammary glands (lactation). Instead the GIT seems to compete very successfully with these tissues for circulating blood EAA.

    KW - stable isotopes

    KW - PROTEIN-SYNTHESIS

    KW - GROWING LAMBS

    KW - WHOLE-BODY

    KW - EFFICIENCY

    KW - METABOLISM

    KW - ABSORPTION

    KW - RUMINANTS

    KW - NITROGEN

    KW - TISSUES

    KW - CONSEQUENCES

    M3 - Article

    VL - 36

    JO - American journal of physiology. Gastrointestinal and liver physiology

    JF - American journal of physiology. Gastrointestinal and liver physiology

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    IS - 6

    ER -