ASSOCIATION BETWEEN UTEROFERRIN, RETINOL-BINDING PROTEIN, AND TRANSFERRIN WITHIN THE UTERINE AND CONCEPTUS COMPARTMENTS DURING PREGNANCY INSWINE

The association between uteroferrin (UF, measured as acid phosphatase [AP] activity), retinol-binding protein (REP), and transferrin (TF) wi thin the intrauterine environment during the estrous cycle and pregnan cy was examined. Pregnant gilts were killed on Days 7, 10, 13, 16, 19, 25, 30, 40, 50, 60, 70, 80, and 90. Cyclic gilts were killed on Days 7, 10, 13, and 16. On Days 7 through 19, each uterine horn was flushed with 20 mi Minimum Essential Medium. On Days 25 through 90, serum and allantoic fluid samples were collected from each fetus within each gi ll and pooled for each gilt. Uterine flushings, allantoic fluid, and f etal serum samples were assayed for AP, REP, and TF. Endometrium was c ollected from all gilts and cultured with [H-3]-leucine; conditioned m edium was measured for nondialyzable radioactive macromolecules, AP, a nd REP. In uterine flushings, AP, REP, and TF were low on Day 7, and t hen increased markedly (p < 0.01) by Day 13 in both cyclic and pregnan t gilts. After log transformation of the data, AP was highly correlate d with REP (r = 0.99) and TF (r = 0.91, p < 0.01). Secretion of REP an d AP by endometrium in culture also increased (p < 0.01) during this p eriod and was similar in cyclic and pregnant gills, and REP and AP sec retion were highly correlated (r = 0.65, p < 0.01). Endometrial tissue did not secrete detectable amounts of TF in culture. Concentrations o f all three proteins were low in allantoic fluid on Day 25, after whic h time they increased to Day 40, and then either stabilized to Day 70 followed by a decrease to Day 90 (AP and TF) or decreased to Day 90 (R EP). Endometrial secretion of both AP and REP increased between Day 25 and 30. Then, AP increased further to Day 40 and did not change to Da y 60, while REP did not change from Day 30 to Day 60. Both decreased f rom Day 60 to 70, did not change to Day 80, and then increased again t o Day 90. The association of REP and TF concentrations with AP in vari ous maternal and conceptus compartments during pregnancy is consistent with the hypothesis that one function of these two proteins may be to protect maternal and fetal tissues from lipid peroxidation that is a possible consequence of iron transport via endometrial secretion of UF .