Effects of restriction of amino acid supply to the isolated perfused guinea-pig mammary gland

Mepham, T. B.; Peters, A. R.; S, Alexandrov

doi:10.1017/s0022029900016861

Cited by 7 publications

(3 citation statements)

References 9 publications

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“…The data represent mean AE SEM of at least three independent experiments. and nutritional studies aimed at examining the role of individual AA in regulating milk-protein synthesis have been performed in vivo [Maas et al, 1997[Maas et al, , 1998Shennan and Peaker, 2000] or in the perfused mammary gland [Mepham et al, 1979]. However, an accurate evaluation of the direct role of single amino acid in the control of milk-protein synthesis has never been possible due to the different uptakes of the individual AA by the gland.…”

Section: Discussionmentioning

confidence: 99%

Role of amino acids in translational mechanisms governing milk protein synthesis in murine and ruminant mammary epithelial cells

Moshel

Rhoads

Barash

2006

J of Cellular Biochemistry

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The role of amino acids (AA) on translational regulation in mammary epithelial cells cultured under lactogenic conditions was studied. The rates of total protein synthesis and beta-lactoglobulin (BLG) synthesis in mouse CID-9 cells were 2.1- or 3.1-fold higher, respectively, than in their bovine L-1 counterparts. Total AA deprivation or selective deprivation of Leu had a negative protein-specific effect on BLG synthesis that was more pronounced in bovine cells than in murine cells. Dephosphorylation of eukaryotic initiation factor 4E-binding protein 1 (4E-BP1) and S6 kinase (S6K1) on Thr(389) but not on Ser(411) was also more prominent in bovine cells. Noteably, deprivation of Leu had a less marked effect on BLG synthesis and 4E-BP1 or S6K1 phosphorylation than deprivation of all AA. In AA-deprived CID-9 cells, Leu specifically restored BLG synthesis from pre-existing mRNA whereas AA also restored total protein synthesis. This restoration was associated with a more pronounced effect on 4E-BP1 and S6K1 phosphorylation in bovine versus murine cells. Rapamycin specifically reduced Leu- and AA-stimulated BLG translation initiation in a dose-dependent manner. A further reduction was observed for Leu-treated cells in the presence of LY294002, a PI3K (phosphatidylinositol 3-kinase) inhibitor, which also reduced total protein synthesis. These findings suggest that direct signaling from AA to the translational machinery is involved in determining the rates of milk protein synthesis in mammary epithelial cells.

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Section: Discussionmentioning

confidence: 99%

Role of amino acids in translational mechanisms governing milk protein synthesis in murine and ruminant mammary epithelial cells

Moshel

Rhoads

Barash

2006

J of Cellular Biochemistry

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“…Mepham and his collaborators (Mepham et al 1979;Mepham, 1982) distinguish 2 groups of essential amino acids (EAA). Group 1 EAA show an apparent stoichiometric transfer to milk protein (i.e.…”

Section: Discussionmentioning

confidence: 99%

“…The branched-chain EAA, besides providing residues for milk protein, seem to play another role as well. Guinea-pig mammary perfusion experiments in which the perfusate was depleted temporarily of individual EAA seemed to have a considerable potential for catabolism of branched-chain EAA (Mepham et al 1979).…”

Section: Discussionmentioning

confidence: 99%

Metabolism of leucine by the isolated perfused goat udder

Roets

Massart-Leën

Peeters

et al. 1983

Journal of Dairy Research

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SUMMARYSeven lactating goat mammary glands from 6 goats were perfused for several hours in the presence of [U-14C]L-leucine (4 experiments) or [2-3H; l-14C]DL-leucine (3 experiments) and received adequate quantities of glucose, acetate and amino acids. Radioactivity in casein was mainly recovered in leucine and 90% of casein leucine was derived from free plasma leucine. About 64% of the leucine molecules were used for casein synthesis. Up to 12% of the molecules were channelled into lipid synthesis, while the remaining (up to 24%) were metabolized to CO2. From the 3H/14C ratio of casein and casein leucine, it was calculated that 70–80% of the leucine molecules were reversibly transaminated before their incorporation into milk protein. However, only 4–8% of the plasma leucine molecules were transaminated during passage through the udder. Different pools for oxidation and for protein synthesis may be present in the goat mammary gland.

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Responses of milk protein, arterial AA concentration, and mammary AA metabolism to graded abomasal casein infusion in lactating goats

Wang

et al. 2007

Small Ruminant Research

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Effects of restriction of amino acid supply to the isolated perfused guinea-pig mammary gland

Cited by 7 publications

References 9 publications

Role of amino acids in translational mechanisms governing milk protein synthesis in murine and ruminant mammary epithelial cells

Role of amino acids in translational mechanisms governing milk protein synthesis in murine and ruminant mammary epithelial cells

Metabolism of leucine by the isolated perfused goat udder

Responses of milk protein, arterial AA concentration, and mammary AA metabolism to graded abomasal casein infusion in lactating goats

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