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.

中文翻译：

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母体营养限制和怀孕初期对牛肉小母牛子宫胎盘组织中中性氨基酸转运蛋白的位置和丰富度的影响。

我们假设母体营养和妊娠天会影响小母牛子宫胎盘组织中中性氨基酸转运蛋白SLC1A1，SLC1A5，SLC7A5，SLC38A2和SLC38A7的丰度。安格斯杂交小母牛（n = 43）发情同步并通过人工授精繁殖。育种时，将小母牛分为两个饮食摄入组之一（CON =达到0.45 kg / d增重的要求的100％或限制的小母牛（RES）= CON摄入量的60％），并在第16、34或50天进行卵巢切除妊娠数= 6至9 / d）。因此，实验设计是一个完全随机的设计，采用2×3的因子处理安排。子宫的横截面取自同侧的角到CL，固定在10％NBF中，切成5 µm，并染色以用于转运蛋白。对于每张图像，分别分析了胎膜（FM ;绒膜尿囊），子宫内膜（ENDO），浅腺（SG），深腺（DG）和子宫肌层（MYO）区域的荧光相对强度，作为转运蛋白的指标丰富。FM的分析仅在第34和50天进行。在ENDO中，与RES母牛相比，CON中的SLC7A5更大（P <0.01）。在SG中，SLC1A1更大（P= 0.02）在第16天的RES中与第16天的CON和第34和50天的RES相比较。在DG中，与妊娠50天相比，SLC1A1在第16天更高（P = 0.02）。在MYO中，第50天CON比第16天CON和第50天RES更大（P = 0.02）。此外，与第16天CON和第34天RES相比，在MYO中，第16天RES的SLC38A2更大（P = 0.02）。在FM中，CON相对于RES的SLC7A5趋向于（P = 0.08）更大。在第16天对所有子宫组织的分析确定，SLC1A1，SLC1A5，SL38A2和SL38A7的表达在不同子宫组织类型之间均存在差异（P <0.01）；但是，只有SLC7A5趋向于（P= 0.10），与RES小母牛相比，CON差异更大。确定天34和50的所有子宫-胎盘组织的分析，认为SLC1A1，SLC7A5，SLC38A2，SLC38A7和分别大于（P ≤0.03）CON与RES小母牛进行比较。此外，在第34天和第50天调查的所有转运蛋白的丰度在子宫胎盘组织类型上也有所不同（P <0.01）。这些数据支持了我们的假设，即从妊娠的第16天到第50天，孕妇的营养和妊娠天会影响子宫胎盘组织中中性氨基酸转运蛋白的含量。此外，这些数据与先前发表的著作相结合，有助于进一步阐明牛小母牛早期妊娠期间的营养供应以及母婴系统的需求。