Submitted to: Biology of Reproduction Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: March 14, 2003
Publication Date: June 1, 2003
Citation: KIM, J.G., VALLET, J.L. CHANGES IN ALLANTOIC FLUID FOLATE BINDING DURING PREGNANCY IN SWINE. BIOLOGY OF REPRODUCTION ABSTRACTS. 2003. v. 68(Suppl. 1). p. 247. Abstract No. 329. Technical Abstract: Porcine endometrium secretes a folate binding protein (FBP) that is likely involved in folate transport to the developing conceptus;however, the secretion of this protein beyond D 15 of pregnancy has not been investigated. Recent evidence suggests that this same protein is present in allantoic fluid on D 60 of pregnancy, thus allantoic fluid folate binding may provide an indication of endometrial secretion rate of FBP during pregnancy. The objective of this study was to measure specific folate binding by allantoic fluid during pregnancy in swine. Allantoic fluid of pregnant White composite gilts (n = 63) was collected on D 20, 35, 50, 70, 90, and 105 (n = 3 to 6 per D). Samples of allantoic fluid were dialyzed against 50 mM glycine, pH 2.8 to remove endogenous folate, followed by dialysis against PBS, pH 7.4. Allantoic fluid samples (10 ul) were then incubated with concentrations of [3H]folate ranging from 0.5 to 4 nM for 16 h at 4 C in the presence or absence of excess unlabeled folate (1 uM) in a total volume of 0.4 ml in PBS. Free folate was removed by incubation with 0.4 ml 0.25% charcoal, 0.025% dextran in 50 mM Tris, pH 8.2 for 15 min followed by centrifugation at 1000 x g for 10 min. An aliquot (0.5 ml) of the resulting supernatant was then used for scintillation counting. The B max and Kd for folate binding was determined for each allantoic fluid sample using nonlinear regression analysis, and then B max and Kd values were analyzed by analysis of variance. The concentration of folate binding sites (B max) increased (P = 0.01) from D 35 (0.63 +/ 0.23 nM) to D 50 (1.58 +/ 0.26), did not differ between d 50 and D 70 (1.41 +/ 0.23), and decreased (P < 0.01) on D 90 (0.26 +/ 0.2). The affinity for folate binding in allantoic fluid (Kd) did not differ between the days measured (mean Kd = 0.19 nM). The results indicate that maximum folate binding in the allantoic fluid occurs between day 50 and 70 of pregnancy and then declines, while the affinity does not change. Because the allantoic fluid may serve as a storage compartment for proteins secreted from endometrium, these differences in allantoic fluid folate binding may reflect changes in endometrial secretion of folate binding protein.