An Estrogen-Dependent Glycoprotein is Synthesized and Released from the Oviduct in a Temporal- and Region-Specific Manner during Early Pregnancy in the Ewe1

Administration of estradiol-17 β (E) to ovariectomized (ovx) sheep results in the synthesis and release of an Mr 90,000−92,000 glycoprotein into the oviductal lumen and into culture medium of ampullar explants (Biol Reprod 1992; 47:889–902). The objective of this study was to determine when and from what region of the oviduct the Mr 90,000−92,000 glycoprotein is synthesized and released during early pregnancy. Estrous ewes were bred to intact rams of known fertility, and oviducts were obtained at estrus (Day 0) and at Days 1.5, 2, 3, 4, 6, and 16 of pregnancy. Pregnancy was verified by the presence of a fertilized egg or developing conceptus and a functional corpus luteum. Oviductal secretions were collected by flushing oviducts with saline and by explant culture. The oviductal fimbria, ampulla, and isthmus were individually cultured (24 h) in the presence of 3H-leucine (3H-leu) or 3H-glucosamine (3H-glcN). The presence of the Mr 90,000−92,000 glycoprotein in oviductal flushings and culture medium was determined by fluorography and Western blotting. The Mr 90,000−92,000 protein was present in SDS gels and blots of oviductal flushings from animals through Days 4–6 of pregnancy, but not in flushings from Day 16 pregnant animals or from ovx, untreated animals. This protein was present in 3H-leu- and 3H-glcN-labeled culture medium of the oviductal ampulla (Days 0, 1.5, 2, 3, 4, 6, and 16) and fimbria (Days 0, 1.5, 2, 3, and 4) during early pregnancy.The Mr 90 000−92 000 protein was not detected in oviductal ampulla or fimbria culture medium obtained from ovx animals, nor was it present in culture medium of the isthmus oviduct obtained from estrous and pregnant animals. These data show that the E-dependent Mr 90 000−92 000 glycoprotein is synthesized and released by the oviduct in a temporally and regionally specific manner during early pregnancy as the gametes and fertilized egg are traversing the tube and prior to a systemic rise in progesterone.