Dietary protein intake and stage of lactation differentially modulate amino acid transporter mRNA abundance in porcine mammary tissue
2009
Laspiur, J. | Burton, J. | Weber, P. | Moore, J. | Kirkwood, R. | Trottier, N.
To test the hypothesis that under restricted and surfeit protein intake the mammary gland undergoes adaptive regulation, changes in mammary tissue mRNA abundance of cationic amino acid (AA) transporter (CAT)-1, CAT-2B, alanine/serine/cysteine/threonine transporter 1 (ASCT1), and broad specificity transporter for neutral and cationic AA (ATB⁰,⁺), and CAT-1 protein abundance were investigated at 2 stages of lactation. Eighteen sows were allocated to a 2 × 3 randomized incomplete block design with 2 stages of lactation (early and peak) and 3 protein levels: deficient (D), adequate (A), or in excess (E) of lactation requirement. In early lactation, compared with A, sows fed E had lower (P = 0.05) piglet growth rate and sows fed D or E had lower (P ≤ 0.05) casein yield. In early lactation, piglet growth rate and milk protein and casein yield increased from D to A and decreased from A to E (quadratic, P = 0.095, P < 0.05, and P < 0.01, respectively). Protein intake did not affect CAT-1, ASCT1, ATB⁰,⁺ mRNA abundance, or CAT-1 protein level. Overall, CAT-2B mRNA abundance decreased linearly with increasing protein intake (P < 0.05). Compared with A, E decreased CAT-2B mRNA abundance (P < 0.05). Compared with early lactation, peak lactation did not increase CAT-1 mRNA abundance or relative CAT-1 protein content, but increased abundance of ASCT1 and ATB⁰,⁺ mRNA (P < 0.01). Mammary CAT-2B appears to be adaptively regulated in vivo at the transcription level, whereas ASCT1 and ATB⁰,⁺ mRNA abundances are associated only with stage of lactation. Neither protein intake nor stage of lactation affects porcine mammary CAT-1 gene expression in vivo.
Mostrar más [+] Menos [-]Juliana Pérez Laspiur, Jeanne L. Burton, Patty S. D. Weber, Julie Moore, Roy N. Kirkwood, and Nathalie L. Trottier
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