Submitted to: Journal of Animal Science Supplement
Publication Type: Abstract Only
Publication Acceptance Date: November 20, 2003
Publication Date: August 1, 2004
Citation: Kim, J.G., Vallet, J.L. 2004. Folate binding protein is secreted by porcine endometrium until placentation in pigs [abstract]. Journal of Animal Science. 82 (Supplement 2):87. (Abstract #240) Technical Abstract: Porcine endometrium secretes folate binding protein (FBP) into the lumen, which is likely involved in folate transport to the developing conceptus. FBP secretion up to D 15 of pregnancy has been reported, but the cellular origin of the FBP and secretion during later pregnancy has not been studied. Thus, the objective of this study was to determine the endometrial localization of the FBP by immunohistochemistry throughout pregnancy. A portion of the uterine walls were collected from D 10, 13 and 15 cyclic and D 10, 13, 15, 20, 35, 50, 70, 90 and 105 pregnant White composite gilts (n=3 to 5) and fixed with 4% paraformaldehyde in PBS. After 16 h, fixed tissues were washed with PBS, changed to 70 % (v/v) ethanol, dehydrated through a graded series of ethanol concentrations, and embedded in paraffin. Uterine wall sections (6 um) were deparaffinized in xylene and rehydrated to water through a graded series of ethanol concentrations. Antigenic sites were revealed by heating the sections in 50 mM Tris, 0.1% SDS and 1% beta-mercaptoethanol. Sections were then incubated with buffer (50 mM Tris, 0.5 M Nacl and 1% Triton X-100) containing 100 ug/ml of either rabbit anti-porcine FBP IgG or normal rabbit serum IgG (both purified using protein A). Localization of bound antibody was determined using the Vectastain Elite ABC reagent with DAB as chromogen. Tissue sections were then counterstained with hematoxylin. In cyclic gilts, immunohistochemical staining of the FBP was present in the endometrial glands on D 10, appeared to be more intense on D 13, and appeared to decrease by D 15. In pregnant gilts, staining was present in the glandular epithelial cells on D 13, 15, and 20, and was absent after D 20. This pattern of FBP staining is consistent with the concept that the secreted form of FBP transports folate to the developing conceptus until the placenta is formed sometime between D 20 and 35 of pregnancy.