IDENTIFICATION AND CHARACTERIZATION OF BOVINE OVIDUCTAL GLYCOPROTEINS SYNTHESIZED AT ESTRUS

Published reports indicate that in several mammalian species the oviduct synthesizes and secretes specific glycoproteins which are components of the luminal fluids at the time of ovulation and fertilization. The present study characterized the secretory glycoproteins synthesized by the bovine oviduct at estrus. Oviducts obtained from four crossbred cows in estrus were flushed with saline, and segments of the ampullary and isthmic regions were fixed for immunocytochemical analyses. The remainder of the tissue was subjected to explant culture for 24 h in medium containing either 3H-leucine or 3H-glucosamine. Analysis of culture media by one- and two-dimensional SDS-PAGE followed by fluorography indicated that both the ampullary and isthmic regions synthesized a major class of M(r) 97000 glycoproteins with isoelectric points ranging from 5.5 to .1. A polyclonal antibody was generated to the glycoproteins after their isolation by gel filtration followed by electrophoretic separation. Western blot analysis of oviductal culture media indicated that the antisera cross-reacted with a doublet at M(r) 97000 and to a lesser extent with two additional bands at M(r) > 200000. Immunoreactive antigens were not identified in serum or in culture media of ovary, uterus, and nonreproductive tract tissues. The M(r) 97000 glycoproteins were present in oviductal flushings obtained from cows in estrus. They were also detected to a lesser degree in oviductal flushings obtained from cows at Days 5, 10, 15, and 18 of the estrous cycle, with the least amount of immunoreactivity being observed in Day 10 samples. Immunocytochemical analysis of oviductal tissue sections at the light microscopic level indicated that immunoperoxidase staining was associated with discrete granular structures found in the apical region of the nonciliated epithelial cells. Colloidal gold immunoelectron microscopy confirmed that the antigens were localized within secretory granules of the secretory cells. These data indicate that the bovine oviductal epithelium synthesizes and secretes a class of oviduct-specific glycoproteins that is present in luminal fluid at the time when fertilization occurs.