The effects of maternal nutrition on the messenger ribonucleic acid expression of neutral and acidic amino acid transporters in bovine uteroplacental tissues from day sixteen to fifty of gestation.

We hypothesized that both day of gestation and maternal nutrition would alter the relative mRNA expression of neutral and acid AA transporters SLC1A1, SLC1A5, SLC7A5, SLC38A2, and SLC38A7. Crossbred Angus heifers (n = 49) were synchronized, bred via AI, assigned to nutritional treatment (100% of NRC requirements for 0.45 kg/d gain [control heifers {CON}] and 60% of CON [restricted heifers {RES}]), and ovariohysterectomized on d 16, 34, or 50 of gestation (n = 6 to 9/d). Nonbred, nonpregnant (NB-NP) controls were ovariohysterectomized on d 16 of the estrous cycle (n = 6) after synchronization. The resulting arrangement was a 2 × 3 factorial + 1 (CON vs. RES × d 16, 34, or 50 + NB-NP controls). Tissues collected included caruncular endometrium (CAR), intercaruncular endometrium (ICAR), fetal membranes (FM; chorioallantois; d 16 and 34), cotyledonary placenta (COT; d 50 only), intercotyledonary placenta (ICOT; d 50 only), and amnion (AMN; d 50 only]). Relative expression of SLC1A1, SLC1A5, SLC7A5, SLC38A2, and SLC38A7 was determined for each tissue using NB-NP CAR and NB-NP ICAR tissues for the baseline; for FM, endometrium from NB-NP controls served as the baseline. In CAR, no day × treatment interaction was observed (P > 0.05). However, day of gestation affected relative expression of SLC1A1, where expression on d 16 was greater (P < 0.01) than expression on d 34 and 50. Additionally, relative expression of SLC38A2 and SLC38A7 was greater (P ≤ 0.05) in pregnant heifers compared with NB-NP heifers. For ICAR, SLC38A7 was influenced by a day × treatment interaction (P < 0.01), where expression in d 16 RES was greater (P ≤ 0.05) than that of any other day or nutritional treatment. Furthermore, expression in d 16 CON was greater (P ≤ 0.05) than that in d 50 RES, with those in d 34 CON and RES and d 50 CON being intermediate. In addition, SLC1A1 was affected by day of gestation, where expression on d 16 was greater (P < 0.01) than that on d 34 and 50. A day × treatment interaction was not observed (P > 0.05) in FM; however, SLC1A5 expression on d 34 was greater (P = 0.02) than on d 50, with that on d 16 being intermediate. Day of gestation also affected expression of SLC38A2, where expression on d 34 and 50 was greater (P < 0.01) than that on d 16. These data support our hypothesis in that both day of gestation and maternal nutrition affected the relative mRNA expression of AA transporter SLC38A7 in ICAR, whereas day of gestation has a greater effect on the relative mRNA expression of other neutral and acidic AA transporters in the various tissues studied. [ABSTRACT FROM AUTHOR]