title: Dietary protein intake and stage of lactation differentially modulate amino acid transporter mRNA abundance in porcine mammary tissue.
abstract: 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 (ATB(0,+)), and CAT-1 protein abundance were investigated at 2 stages of lactation. Eighteen sows were allocated to a 2 x 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 < or = 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, ATB(0,+) 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 ATB(0,+) mRNA (P < 0.01). Mammary CAT-2B appears to be adaptively regulated in vivo at the transcription level, whereas ASCT1 and ATB(0,+) 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.
authors.affiliation: Department of Animal Science and 5Department of Large Animal Clinical Science, Michigan State University, East Lansing, MI 48824, USA.
authors.forename: Juliana Pérez
authors.initials: JP
authors.lastname: Laspiur
authors.forename: Jeanne L
authors.initials: JL
authors.lastname: Burton
authors.forename: Patty S D
authors.initials: PS
authors.lastname: Weber
authors.forename: Julie
authors.initials: J
authors.lastname: Moore
authors.forename: Roy N
authors.initials: RN
authors.lastname: Kirkwood
authors.forename: Nathalie L
authors.initials: NL
authors.lastname: Trottier
mesh_terms: D026905:Amino Acid Transport Systems / Q000235:genetics / Q000378:metabolism*; D000596:Amino Acids / Q000378:metabolism*; D000818:Animals; D000831:Animals, Newborn / Q000254:growth & development; D002364:Caseins / Q000378:metabolism; D004032:Diet; D004044:Dietary Proteins / Q000008:administration & dosage / Q000378:metabolism*; D005260:Female; D007774:Lactation / Q000378:metabolism*; D008321:Mammary Glands, Animal / Q000378:metabolism*; D008892:Milk / Q000378:metabolism*; D011488:Protein Deficiency / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D011897:Random Allocation; D013552:Swine; D015430:Weight Gain
chemical_list: D026905:Amino Acid Transport Systems; D000596:Amino Acids; D002364:Caseins; D004044:Dietary Proteins; D012333:RNA, Messenger