Transcript abundance of amino acid transporters, β-casein, and α-lactalbumin in mammary tissue of periparturient, lactating, and postweaned sows

Abstract The objective of these experiments was to test the hypothesis that transcript abundance of cationic AA transporter- and milk protein-encoding genes increase in the porcine mammary gland in response to higher lactation demand. Genes of interest included those encoding for the milk proteins α-lactalbumin (α-LA) and β-casein (β-CN; LALBA and CSN2 , respectively), and AA transporter b 0,+ AT, y + LAT1, y + LAT2, ATB 0,+ , CAT-1, and CAT-2b ( SLC7A9 , SLC7A7 , SLC7A6 , SLC6A14 , SLC7A1 , and SLC7A2 , respectively). Mammary tissue was biopsied from 4 sows on d 110 of gestation (prepartum), on d 2 (early postpartum), on d 5 (early), and d 17 (peak) of lactation, and on d 5 after weaning (postweaning), and mRNA of target genes quantified by reverse transcription quantitative PCR. Compared with prepartum, CAT-1, ATB 0,+ , y + LAT2, β-CN, and α-LA mRNA abundance was higher at early lactation, whereas compared with early lactation, only CAT-1 and α-LA mRNA abundance was higher at peak lactation. The CAT-2b, y + LAT1, and b 0,+ AT mRNA abundance did not differ when comparing either prepartum or peak lactation to early lactation. Compared with peak lactation, postweaning mRNA abundance of CAT-1, ATB 0,+ , α-LA, and β-CN decreased, y + LAT2, CAT-2b, and b 0,+ AT remained unchanged, and y + LAT1 increased. The mRNA abundance of y + LAT2 increased from early postpartum to early lactation, and remained unchanged for CAT-1, ATB 0,+ , α-LA, and β-CN. From prepartum to peak lactation, the mRNA abundance of CAT-1, y + LAT2, and ATB 0,+ was positively correlated with that of β-CN and α-LA. In conclusion, the expression of genes encoding for y + LAT1, CAT-2b, and b 0,+ AT remained unchanged in porcine mammary glands over prepartum to peak lactation period, whereas expression of genes encoding for CAT-1, ATB 0,+ , and y + LAT2 was upregulated and positively correlated to expression of genes encoding for the mammary synthesized milk proteins β-CN and α-LA.