Select nutrients in the ovine uterine lumen. IV. Expression of neutral and acidic amino acid transporters in ovine uteri and peri-implantation conceptuses.

The availability of specific neutral and acidic amino acids in the uterine lumen of ewes increased significantly during the peri-implantation period, but mechanisms for their transport into the uterine lumen and uptake by conceptuses are not established in any species. In this study, effects of pregnancy, progesterone (P4), and interferon tau (IFNT) on expression of neutral and acidic amino acid transporters in uteri of cyclic and pregnant ewes and conceptuses were studied. SLC1A2, SLC1A3, SLC3A1, SLC6A14, SLC6A19, SLC7A6, SLC38A3, and SLC38A6 mRNAs were only weakly expressed in the ovine endometrium. However, SLC1A4, SLC1A5, SLC7A8, and SLC43A2 mRNAs were detectable in uterine luminal epithelia (LE), superficial glandular epithelia (sGE), and/or glandular epithelia (GE). SLC1A1 and SLC7A5 mRNAs were most abundant in LE/sGE and GE. SLC1A3 and SLC38A4 mRNAs were most abundant in uterine stroma. SLC38A6 mRNA was detected only in cells with a stromal distribution suggesting immune lineage. SLC1A5 mRNA was expressed primarily in LE/sGE and stromal cells, and it was more abundant in uteri of pregnant ewes (day x status interaction; P < 0.05). Furthermore, P4 induced and IFNT further stimulated SLC1A5 expression in LE/sGE. Endometrial SLC1A1, SLC7A5, and SLC43A2 mRNAs demonstrated both temporal and cellSLC-specific changes. Several mRNAs were detectable in trophectoderm (SLC6A19, SLC7A5, SLC7A6, and SLC43A2), while others were more abundant in endoderm (SLC1A4, SLC1A5, SLC6A19, SLC7A5, SLC7A6, SLC7A8, and SLC43A2) of conceptuses. These results document coordinate changes in expression of transporters that are likely responsible for increases in amounts of neutral and acidic amino acids in the uterine lumen to support conceptus growth, development, and survival.