Select nutrients in the ovine uterine lumen. I. Amino acids, glucose, and ions in uterine lumenal flushings of cyclic and pregnant ewes.

Nutrients in uterine secretions are essential for development and survival of conceptuses (embryo and associated extraembryonic membranes) during pregnancy; however, little is known about changes in the amounts of specific nutrients in the uterine fluids of cyclic and pregnant ruminants. This study determined quantities of glucose, amino acids, glutathione, calcium, sodium, and potassium in uterine lumenal fluid from cyclic (Days 3-16) and pregnant (Days 10-16) ewes. Total recoverable glucose, Arg, Gln, Leu, Asp, Glu, Asn, His, beta-Ala, Tyr, Trp, Met, Val, Phe, Ile, Lys, Cys, Pro, glutathione, calcium, and sodium were greater in the uterine fluid of pregnant compared with cyclic ewes between Days 10 and 16. In cyclic ewes, only modest changes in the total amounts of glucose, Asn, Cit, Tyr, Trp, Met, Val, Cys, glutathione, calcium, and potassium were detected between Days 3 and 16. However, in pregnant ewes, amounts of glucose, Arg, Gln, Glu, Gly, Cys, Leu, Pro, glutathione, calcium, and potassium in uterine fluids increased 3- to 23-fold between Days 10 and 14 and remained high to Day 16. Of particular interest were increases in glucose, Arg, Leu, and Gln in uterine flushings of pregnant ewes between Days 10 and 16 of pregnancy. Total amounts of His, ornithine, Lys, Ser, Thr, Ile, Phe, Trp, Met, and Cit in uterine fluids also increased, but to a lesser extent during early pregnancy. These novel results indicate activation of pregnancy-associated mechanisms for transport of nutrients into the uterine lumen, and they provide a framework for future studies of nutrients, including glucose, amino acids, and glutathione, required to activate nutrient-sensing cell signaling pathways for growth, development, and survival of conceptuses, as well as for optimization of culture media for in vitro studies of conceptus development.