Department of Animal Sciences, Center for Nutrition and Pregnancy, North Dakota State University, Fargo, ND.
Department of Animal Science, University of Tennessee, Knoxville, TN.
J Anim Sci. 2020 Jul 1;98(7). doi: 10.1093/jas/skaa197.
We hypothesized that maternal nutrition and day of gestation would influence the abundance of the neutral amino acid transporters SLC1A1, SLC1A5, SLC7A5, SLC38A2, and SLC38A7 in heifer utero-placental tissues. Angus-cross heifers (n = 43) were estrus synchronized and bred via AI. At breeding, heifers were assigned to one of two dietary intake groups (CON = 100% of requirements to achieve 0.45 kg/d gain or restricted heifers (RES) = 60% of CON intake) and ovariohysterectomized on day 16, 34, or 50 of gestation (n = 6 to 9/d). Thus, the experimental design was a completely randomized design with a 2 × 3 factorial arrangement of treatments. Uterine cross sections were taken from the horn ipsilateral to the CL, fixed in 10% NBF, sectioned at 5 µm, and stained for transporters. For each image, the areas of fetal membrane (FM; chorioallantois), endometrium (ENDO), superficial glands (SG), deep glands (DG), and myometrium (MYO) were analyzed separately for relative intensity of fluorescence as an indicator of transporter abundance. Analysis of FM was only conducted on days 34 and 50. In ENDO, SLC7A5 was greater (P < 0.01) in CON compared with RES heifers. In SG, SLC1A1 was greater (P = 0.02) in day 16 RES compared with day 16 CON and days 34 and 50 RES. In DG, SLC1A1 was greater (P = 0.02) on day 16 compared with 50 of gestation. In MYO, SLC1A1 was greater (P = 0.02) in day 50 CON compared with day 16 CON and day 50 RES. Additionally, in MYO SLC38A2 was greater (P = 0.02) in day 16 RES compared with day 16 CON and day 34 RES. In FM, SLC7A5 tended (P = 0.08) to be greater in CON vs RES. Analysis of all uterine tissues on day 16 determined that expression of SLC1A1, SLC1A5, SL38A2, and SL38A7 differed across uterine tissue type (P < 0.01); however, only SLC7A5 tended (P = 0.10) to differ and be greater in CON compared with RES heifers. Analysis of all utero-placental tissues on days 34 and 50 determined that SLC1A1, SLC7A5, SLC38A2, and SLC38A7 were greater (P ≤ 0.03) in CON compared with RES heifers. Furthermore, abundance of all transporters investigated on days 34 and 50 differed across utero-placental tissue types (P < 0.01). These data support our hypothesis that maternal nutrition and day of gestation influence the abundance of neutral amino acid transporters in utero-placental tissues from days 16 to 50 of gestation. Additionally, these data combined with previously published works help further elucidate nutrient supply and demands of the maternal and fetal system during early gestation in beef heifers.
我们假设母体营养和妊娠天数会影响中性氨基酸转运体 SLC1A1、SLC1A5、SLC7A5、SLC38A2 和 SLC38A7 在小母牛子宫胎盘组织中的丰度。 Angus 杂交小母牛（n = 43）被发情同步并通过人工授精配种。在配种时，小母牛被分配到两个饮食摄入组之一（CON = 满足 0.45 kg/d 增重需求的 100%或限制采食的小母牛（RES）= CON 摄入的 60%），并在妊娠第 16、34 或 50 天进行卵巢子宫切除术（n = 6 至 9/天）。因此，实验设计是一个完全随机设计，具有 2 × 3 因子处理的安排。从角同侧的 CL 取子宫横断面，用 10% NBF 固定，切成 5 µm 厚的切片，并对转运体进行染色。对于每个图像，分别分析胎儿膜（FM；绒毛尿囊膜）、子宫内膜（ENDO）、浅层腺体（SG）、深层腺体（DG）和子宫肌层（MYO）的荧光强度区域，作为转运体丰度的指标。仅在妊娠第 34 和 50 天对 FM 进行分析。在 ENDO 中，CON 组的 SLC7A5 高于 RES 组（P < 0.01）。在 SG 中，第 16 天 RES 的 SLC1A1 高于第 16 天 CON 和第 34 天和第 50 天 RES（P = 0.02）。在 DG 中，第 16 天的 SLC1A1 高于第 50 天的妊娠（P = 0.02）。在 MYO 中，第 50 天 CON 的 SLC1A1 高于第 16 天 CON 和第 50 天 RES（P = 0.02）。此外，在 MYO 中，第 16 天 RES 的 SLC38A2 高于第 16 天 CON 和第 34 天 RES（P = 0.02）。在 FM 中，CON 组的 SLC7A5 高于 RES 组（P = 0.08）。在第 16 天对所有子宫组织进行分析，确定 SLC1A1、SLC1A5、SL38A2 和 SL38A7 在子宫组织类型上存在差异（P < 0.01）；然而，只有 SLC7A5 有趋势（P = 0.10），且在 CON 组中高于 RES 组。在第 34 天和第 50 天对所有子宫胎盘组织进行分析，确定 SLC1A1、SLC7A5、SLC38A2 和 SLC38A7 在 CON 组中高于 RES 组（P ≤ 0.03）。此外，第 34 天和第 50 天所有转运体的丰度在子宫胎盘组织类型上存在差异（P < 0.01）。这些数据支持我们的假设，即母体营养和妊娠天数会影响妊娠第 16 天至第 50 天子宫胎盘组织中中性氨基酸转运体的丰度。此外，这些数据与之前发表的研究结果相结合，有助于进一步阐明肉牛小母牛妊娠早期母体和胎儿系统的营养供应和需求。
