Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 27, 1999
Publication Date: N/A
Interpretive Summary: The vitamin, folate is required for cell replication. Thus, rapidly dividing cells require greater amounts of folate. The cells of the embryo divide rapidly during early pregnancy. During later pregnancy, fetal cells which ultimately become red blood cells also divide rapidly. Recent work by our laboratory demonstrated that folate is likely delivered to the developing swine embryo via attachment to a protein, folate binding protein. In the current experiment, a sensitive, accurate, and specific assay was developed for this protein. Using this assay, we demonstrated that the increase in folate binding protein production by the uterus is unaffected by the conceptus, and is accelerated by early progesterone treatment. The assay will improve our ability to study this protein in detail, including factors, like progesterone treatment, which can either increase or decrease secretion; thus, increasing or decreasing folate delivery to the swine embryo. Several experiments suggest that improved folate delivery during pregnancy may be beneficial to embryonic survival and, therefore, may increase litter size.
Technical Abstract: A radioimmunoassay (RIA) was developed for porcine intrauterine folate binding protein (FBP). Displacement of [125I]-FBP caused by increasing dilutions of intrauterine flushings or endometrial culture media were parallel to the displacement caused by standards. Known amounts of purified allantoic fluid FBP to dilutions of either intrauterine flushings or endometrial culture medium were measured accurately by the RIA. To test specificity, 2 mL samples of uterine flushings collected from d 15 pregnant and nonpregnant gilts were preincubated with 10 uCi H-folic acid and then chromatographed using Sephadex G-100. The fractions were subsequently assayed for radioactivity by scintillation counting and for FBP by RIA. The [3H]-folic acid and FBP peaks coincided indicating that the RIA is specific for FBP. Uterine flushings were collected on d 10, 11, 12, 13, 14 and 15 of the cycle or pregnancy from (1) white crossbred, (2) white crossbred progesterone treated (200 mg progesterone at 48 and 72 h after estrus), and (3) Meishan gilts and assayed for FBP. Total FBP increased 140-fold from d 10 to 15, and the pattern of change across day did not differ between pregnant and nonpregnant gilts. Progesterone treatment increased intrauterine FBP content on d 10 and 11. These results indicate that the RIA for FBP is valid. The onset of FBP secretion by the uterus that occurs between d 10 and 15 of the cycle or pregnancy is influenced by the duration of progesterone influence.