Vascular sources of phenylalanine, tyrosine, lysine, and methionine for casein synthesis in lactating goats

B J Bequette, F R Backwell, C E Kyle, Alexander Graham Calder, Vivien Buchan, L A Crompton, J France, J C MacRae

    Research output: Contribution to journalArticle

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    Abstract

    The contribution to casein biosynthesis of peptides derived from blood was examined in late lactation goats (254 to 295 d in milk). Ratios of mammary uptake of free amino acids (AA) in blood to output of AA in milk protein and ratios of the enrichments of Phe, Tyr, Met, and Lys at isotopic plateau in secreted milk casein to the free AA in arterial and mammary vein blood were monitored during the last 5 h of a 30-h continuous i.v. infusion of [1-13C]Phe, [2H4]Tyr, [5-13CH3]Met, and [2-15N]Lys on two occasions: before (control) and on d 6 of an i.v. infusion of Phe (6 g/d). During the control, uptakes of free Phe and Met were less than their output in milk. This result was comparable with the labeling kinetic results, suggesting that vascular peptides contributed 5 to 11% of Phe and 8 to 18% of Met. Free Tyr and Lys uptakes during the control were sufficient for milk output; however, the labeling kinetics indicated that 13 to 25% of the Tyr and 4 to 13% of the Lys were derived from peptides. Infusion of Phe increased the uptake of free AA but reduced the contribution of peptides toward Phe (0 to 3%) and Tyr (8 to 14%) supply for casein synthesis. Whole body hydroxylation of Phe to Tyr increased from 10 to 18% with the infusion of Phe; within the mammary gland, this conversion was lower (3 to 5%). Results suggest that the mammary utilization of peptides containing Phe and Tyr appears to depend on the supply of free AA in blood.
    Original languageEnglish
    Pages (from-to)362-377
    Number of pages16
    JournalJournal of Dairy Science
    Volume82
    Issue number2
    DOIs
    Publication statusPublished - 1 Feb 1999

    Fingerprint

    Caseins
    Phenylalanine
    blood vessels
    Goats
    phenylalanine
    Methionine
    Lysine
    Blood Vessels
    Tyrosine
    tyrosine
    methionine
    casein
    lysine
    goats
    free amino acids
    peptides
    Milk
    Amino Acids
    synthesis
    breasts

    Keywords

    • Animals
    • Carbon Isotopes
    • Caseins
    • Deuterium
    • Female
    • Goats
    • Hydroxylation
    • Kinetics
    • Lactation
    • Lysine
    • Mammary Glands, Animal
    • Methionine
    • Phenylalanine
    • Tyrosine
    • mammary gland
    • peptides
    • casein synthesis
    • goats

    Cite this

    Bequette, B. J., Backwell, F. R., Kyle, C. E., Calder, A. G., Buchan, V., Crompton, L. A., ... MacRae, J. C. (1999). Vascular sources of phenylalanine, tyrosine, lysine, and methionine for casein synthesis in lactating goats. Journal of Dairy Science, 82(2), 362-377. https://doi.org/10.3168/jds.S0022-0302(99)75243-4

    Vascular sources of phenylalanine, tyrosine, lysine, and methionine for casein synthesis in lactating goats. / Bequette, B J; Backwell, F R; Kyle, C E; Calder, Alexander Graham; Buchan, Vivien; Crompton, L A; France, J; MacRae, J C.

    In: Journal of Dairy Science, Vol. 82, No. 2, 01.02.1999, p. 362-377.

    Research output: Contribution to journalArticle

    Bequette, BJ, Backwell, FR, Kyle, CE, Calder, AG, Buchan, V, Crompton, LA, France, J & MacRae, JC 1999, 'Vascular sources of phenylalanine, tyrosine, lysine, and methionine for casein synthesis in lactating goats', Journal of Dairy Science, vol. 82, no. 2, pp. 362-377. https://doi.org/10.3168/jds.S0022-0302(99)75243-4
    Bequette, B J ; Backwell, F R ; Kyle, C E ; Calder, Alexander Graham ; Buchan, Vivien ; Crompton, L A ; France, J ; MacRae, J C. / Vascular sources of phenylalanine, tyrosine, lysine, and methionine for casein synthesis in lactating goats. In: Journal of Dairy Science. 1999 ; Vol. 82, No. 2. pp. 362-377.
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    title = "Vascular sources of phenylalanine, tyrosine, lysine, and methionine for casein synthesis in lactating goats",
    abstract = "The contribution to casein biosynthesis of peptides derived from blood was examined in late lactation goats (254 to 295 d in milk). Ratios of mammary uptake of free amino acids (AA) in blood to output of AA in milk protein and ratios of the enrichments of Phe, Tyr, Met, and Lys at isotopic plateau in secreted milk casein to the free AA in arterial and mammary vein blood were monitored during the last 5 h of a 30-h continuous i.v. infusion of [1-13C]Phe, [2H4]Tyr, [5-13CH3]Met, and [2-15N]Lys on two occasions: before (control) and on d 6 of an i.v. infusion of Phe (6 g/d). During the control, uptakes of free Phe and Met were less than their output in milk. This result was comparable with the labeling kinetic results, suggesting that vascular peptides contributed 5 to 11{\%} of Phe and 8 to 18{\%} of Met. Free Tyr and Lys uptakes during the control were sufficient for milk output; however, the labeling kinetics indicated that 13 to 25{\%} of the Tyr and 4 to 13{\%} of the Lys were derived from peptides. Infusion of Phe increased the uptake of free AA but reduced the contribution of peptides toward Phe (0 to 3{\%}) and Tyr (8 to 14{\%}) supply for casein synthesis. Whole body hydroxylation of Phe to Tyr increased from 10 to 18{\%} with the infusion of Phe; within the mammary gland, this conversion was lower (3 to 5{\%}). Results suggest that the mammary utilization of peptides containing Phe and Tyr appears to depend on the supply of free AA in blood.",
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    T1 - Vascular sources of phenylalanine, tyrosine, lysine, and methionine for casein synthesis in lactating goats

    AU - Bequette, B J

    AU - Backwell, F R

    AU - Kyle, C E

    AU - Calder, Alexander Graham

    AU - Buchan, Vivien

    AU - Crompton, L A

    AU - France, J

    AU - MacRae, J C

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    N2 - The contribution to casein biosynthesis of peptides derived from blood was examined in late lactation goats (254 to 295 d in milk). Ratios of mammary uptake of free amino acids (AA) in blood to output of AA in milk protein and ratios of the enrichments of Phe, Tyr, Met, and Lys at isotopic plateau in secreted milk casein to the free AA in arterial and mammary vein blood were monitored during the last 5 h of a 30-h continuous i.v. infusion of [1-13C]Phe, [2H4]Tyr, [5-13CH3]Met, and [2-15N]Lys on two occasions: before (control) and on d 6 of an i.v. infusion of Phe (6 g/d). During the control, uptakes of free Phe and Met were less than their output in milk. This result was comparable with the labeling kinetic results, suggesting that vascular peptides contributed 5 to 11% of Phe and 8 to 18% of Met. Free Tyr and Lys uptakes during the control were sufficient for milk output; however, the labeling kinetics indicated that 13 to 25% of the Tyr and 4 to 13% of the Lys were derived from peptides. Infusion of Phe increased the uptake of free AA but reduced the contribution of peptides toward Phe (0 to 3%) and Tyr (8 to 14%) supply for casein synthesis. Whole body hydroxylation of Phe to Tyr increased from 10 to 18% with the infusion of Phe; within the mammary gland, this conversion was lower (3 to 5%). Results suggest that the mammary utilization of peptides containing Phe and Tyr appears to depend on the supply of free AA in blood.

    AB - The contribution to casein biosynthesis of peptides derived from blood was examined in late lactation goats (254 to 295 d in milk). Ratios of mammary uptake of free amino acids (AA) in blood to output of AA in milk protein and ratios of the enrichments of Phe, Tyr, Met, and Lys at isotopic plateau in secreted milk casein to the free AA in arterial and mammary vein blood were monitored during the last 5 h of a 30-h continuous i.v. infusion of [1-13C]Phe, [2H4]Tyr, [5-13CH3]Met, and [2-15N]Lys on two occasions: before (control) and on d 6 of an i.v. infusion of Phe (6 g/d). During the control, uptakes of free Phe and Met were less than their output in milk. This result was comparable with the labeling kinetic results, suggesting that vascular peptides contributed 5 to 11% of Phe and 8 to 18% of Met. Free Tyr and Lys uptakes during the control were sufficient for milk output; however, the labeling kinetics indicated that 13 to 25% of the Tyr and 4 to 13% of the Lys were derived from peptides. Infusion of Phe increased the uptake of free AA but reduced the contribution of peptides toward Phe (0 to 3%) and Tyr (8 to 14%) supply for casein synthesis. Whole body hydroxylation of Phe to Tyr increased from 10 to 18% with the infusion of Phe; within the mammary gland, this conversion was lower (3 to 5%). Results suggest that the mammary utilization of peptides containing Phe and Tyr appears to depend on the supply of free AA in blood.

    KW - Animals

    KW - Carbon Isotopes

    KW - Caseins

    KW - Deuterium

    KW - Female

    KW - Goats

    KW - Hydroxylation

    KW - Kinetics

    KW - Lactation

    KW - Lysine

    KW - Mammary Glands, Animal

    KW - Methionine

    KW - Phenylalanine

    KW - Tyrosine

    KW - mammary gland

    KW - peptides

    KW - casein synthesis

    KW - goats

    U2 - 10.3168/jds.S0022-0302(99)75243-4

    DO - 10.3168/jds.S0022-0302(99)75243-4

    M3 - Article

    C2 - 10068958

    VL - 82

    SP - 362

    EP - 377

    JO - Journal of Dairy Science

    JF - Journal of Dairy Science

    SN - 0022-0302

    IS - 2

    ER -