Regulation of amino acid transporters in the mammary gland from late pregnancy to peak lactation in the sow

Abstract 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 mRNA 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