Arginine, Leucine, and Glutamine Stimulate Proliferation of Porcine Trophectoderm Cells Through the MTOR-RPS6K-RPS6-EIF4EBP1 Signal Transduction Pathway1

During the peri-implantation and early placentation periods in pigs, conceptuses (embryo and its extra-embryonic mem-branes) undergo dramatic morphological changes and differen-tiation that require the exchange of nutrients (histotroph) and gasses across the trophectoderm and a true epitheliochorial placenta. Of these nutrients, arginine (Arg), leucine (Leu), and glutamine (Gln) are essential components of histotroph; howev-er, little is known about changes in their total amounts in the uterine lumen of cyclic and pregnant gilts and their effects on cell signaling cascades. Therefore, we determined quantities of Arg, Leu, and Gln in uterine luminal fluids and found that total recoverable amounts of these amino acids increased in pregnant but not cyclic gilts between Days 12 and 15 after onset of estrus. We hypothesized that Arg, Leu, and Gln have differential effect