摘要
Background: Milk protein is crucial for milk quality in sows and health of newborn piglets. Plasma amino acids(AA)in sows are important precursors for milk protein synthesis in the mammary gland. In order to study the regulation of AA transported in sow mammary glands and possible underlying mechanisms, we measured the expression of genes coding for milk proteins, AA transporter expressions, and plasma AA concentrations in sows at three different physiological stages(D-17, D1 and D17 of lactation), and then further investigated the regulation of AA transport across the cell membrane by adaptive mechanisms using pig mammary epithelial cells(PMEC) as an in vitro model.PMEC were cultured in DMEM:F12 with 4 amino acid concentrations(0 × AA complex, 1 × AA complex, 5 × AA complex,and 25 × AA complex). Classes of AA complexes evaluated in this study included neutral AAs(L-Ala + L-Ser + L-Cys), acidic AAs(L-Asp, L-Glu) and neutral + basic AAs(L-Ala + L-Ser + L-Cys + L-Lys).Results: Our results indicated that m RNA expression of genes coding for milk protein(αs1-casein, αs2-casein,β-casein and κ-casein) increased significantly with the advance of physiological stage(P < 0.05), and plasma concentrations of most AAs including threonine, serine, glutamate, alanine, valine, cysteine, methionine, isoleucine and tyrosine were greater at D1 of lactation compared with D-17 and D17 of lactation(P < 0.05). Additionally, protein and gene expressions of AA transporters including excitatory AA transporter 3(EAAT3), alanine/serine/cysteine/threonine transporter(ASCT1) and sodium-coupled neutral AA transporter 1(SNAT2) were greater in lactating sow mammary glands compared with sow mammary glands in late pregnancy(P < 0.05). The m RNA expressions of SLC38 A2, SLC1 A1,SLC6 A14 increased significantly in the cell mediums supplemented with 5 × and 25 × of AA complexes compared with those cells cultured in DMEM/F12 cell medium(P < 0.05). The m RNA expressions of SLC38 A, SLC1 A4, and SLC6 A14 also increased in EBSS cell medium compared to DMEM/F12. However, only m RNA expression of SLC38 A decreased when AA complex was added into EBSS(P < 0.05).Conclusion: AA transportation was positively regulated in sow mammary glands with the advance of physiological stage from late pregnancy to peak of lactation and AA transporters in PMECs were adaptively regulated by changed AA concentrations.
Background: Milk protein is crucial for milk quality in sows and health of newborn piglets. Plasma amino acids(AA)in sows are important precursors for milk protein synthesis in the mammary gland. In order to study the regulation of AA transported in sow mammary glands and possible underlying mechanisms, we measured the expression of genes coding for milk proteins, AA transporter expressions, and plasma AA concentrations in sows at three different physiological stages(D-17, D1 and D17 of lactation), and then further investigated the regulation of AA transport across the cell membrane by adaptive mechanisms using pig mammary epithelial cells(PMEC) as an in vitro model.PMEC were cultured in DMEM:F12 with 4 amino acid concentrations(0 × AA complex, 1 × AA complex, 5 × AA complex,and 25 × AA complex). Classes of AA complexes evaluated in this study included neutral AAs(L-Ala + L-Ser + L-Cys), acidic AAs(L-Asp, L-Glu) and neutral + basic AAs(L-Ala + L-Ser + L-Cys + L-Lys).Results: Our results indicated that m RNA expression of genes coding for milk protein(αs1-casein, αs2-casein,β-casein and κ-casein) increased significantly with the advance of physiological stage(P < 0.05), and plasma concentrations of most AAs including threonine, serine, glutamate, alanine, valine, cysteine, methionine, isoleucine and tyrosine were greater at D1 of lactation compared with D-17 and D17 of lactation(P < 0.05). Additionally, protein and gene expressions of AA transporters including excitatory AA transporter 3(EAAT3), alanine/serine/cysteine/threonine transporter(ASCT1) and sodium-coupled neutral AA transporter 1(SNAT2) were greater in lactating sow mammary glands compared with sow mammary glands in late pregnancy(P < 0.05). The m RNA expressions of SLC38 A2, SLC1 A1,SLC6 A14 increased significantly in the cell mediums supplemented with 5 × and 25 × of AA complexes compared with those cells cultured in DMEM/F12 cell medium(P < 0.05). The m RNA expressions of SLC38 A, SLC1 A4, and SLC6 A14 also increased in EBSS cell medium compared to DMEM/F12. However, only m RNA expression of SLC38 A decreased when AA complex was added into EBSS(P < 0.05).Conclusion: AA transportation was positively regulated in sow mammary glands with the advance of physiological stage from late pregnancy to peak of lactation and AA transporters in PMECs were adaptively regulated by changed AA concentrations.
基金
financially supported by the National Natural Science Foundation of China(No.31402082)
