In vitro incubation of golden (syrian) hamster ovarian oocytes and human sperm with a human oviduct specific glycoprotein

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Abstract
The objective of this study was to determine if human oviduct specific glycoprotein (huOGP) would associate with hamster ovarian oocytes and human sperm during in vitro incubation. The huOGP used in these studies was partially purified from human hydrosalpinx fluid. Hamster ovarian oocytes and human sperm samples were incubated in culture medium with and without huOGP. Association of huOGP was assessed by indirect immunofluorescence assay using a polyclonal antibody prepared against huOGP. Intense fluorescence of the zona pellucida, and bright but uneven fluorescence of the perivitelline space, were observed in hamster ovarian oocytes following incubation in the presence of huOGP. A similar but more uniform pattern of fluorescence was observed when hamster oviductal oocytes (positive controls) were incubated in culture medium alone. Fluorescence was absent when oocytes were assayed with preimmune serum. The association of huOGP with the zona pellucida and perivitelline space appeared to be specific since thyroglobulin, a large molecular weight glycoprotein, and human serum albumin, the major protein in oviduct fluid, did not associate with the hamster oocytes nor inhibit huOGP association when included in the culture medium. Fluorescence was absent when human sperm incubated with huOGP were assayed with antiserum to huOGP. However, human sperm fluoresced when incubated with a uterine glycoprotein, CUPED, which had previously been shown to bind to cat sperm during in vitro incubation. Sperm also fluoresced brightly when human sperm antibody was used as a positive control. Solubilization of sperm membrane proteins postincubation and analysis of these proteins by 1‐D SDS‐PAGE followed by immunoblotting also failed to show an association of huOGP with human sperm. Electron microscopy of sperm both pre‐ and postsolubilization confirmed that the sperm membranes were removed by this process. In conclusion, the association of huOGP with hamster oocytes in vitro suggests that huOGP may associate with human oocytes in vivo, whereas that may not be true for human sperm in vivo. The association of huOGP with oocytes may serve to facilitate the process of fertilization and early embryonic development within the oviduct.