0001 Effects of maternal nutritional status on nutrient transporter expression in bovine utero-placental tissue on days 16 to 50 of gestation

We hypothesized that maternal nutrition and day of gestation would impact mRNA expression of nutrient transporters GLUT1, CAT-1, CAT-2, and CAT-3 in beef heifers. Crossbred Angus heifers (n = 49) were synchronized, bred via AI, assigned to nutritional treatment (CON = 100% of requirements for 0.45 kg/d gain and RES = 60% of CON) and ovariohysterectomized on d 16, 34, or 50 of gestation (n = 6 to 9/d); nonpregnant (NP) controls were not bred and ovariohysterectomized on d 16 of the synchronized estrous cycle (n = 6). The resulting arrangement of treatments was a 2 × 3 factorial + 1. Caruncle (CAR), intercaruncular endometrium (ICAR), and fetal membranes (FM), were obtained from the pregnant uterine horn immediately following ovariohysterectomy. For NP controls, only CAR and ICAR were obtained. Relative expression of the glucose transporter GLUT1 and cationic amino acid transporters CAT-1, CAT-2, and CAT-3 was determined for each tissue utilizing NP-CAR and NP-ICAR tissue as the baseline. For FM, NP endometrium served as the baseline. There was no interaction of day and treatment in FM for any genes (P ≥ 0.05). Expression of GLUT1 and CAT-1 both showed a day effect, being greater (P < 0.05) in FM on d 34 and 50, compared with d 16. In CAR there was no day × treatment interaction and CAT-3 expression tended (P = 0.06) to be greater in CON vs. RES heifers. Additionally, expression of GLUT1, CAT-1, and CAT-2 in CAR were greater (P < 0.01) on d 16 compared with d 34 and 50, d 34 compared with d 50, and d 16 and 34 compared with d 50, respectively. In ICAR, CAT-2 showed a day × treatment interaction, being greater (P = 0.01) on d 50 CON compared with all other groups. Transporter CAT-3 tended (P = 0.09) to be greater in day × treatment in ICAR on d 16 CON compared with all other days and treatments. The expression of GLUT1 was greater (P < 0.01) in ICAR on d 16 than all other days. Arginine transporter CAT-1 was greater (P < 0.01) in ICAR on d 34 and 50 compared with d 16. These results partially support our hypothesis and indicate that day was a more influential factor for mRNA expression of utero-placental glucose and cationic amino acid transporters than maternal nutritional status in heifers during early pregnancy.