EARLY EMBRYONIC-DEVELOPMENT IN THE DJUNGARIAN HAMSTER (PHODOPUS-SUNGORUS) IS ACCOMPANIED BY ALTERATIONS IN THE DISTRIBUTION AND INTENSITY OF AN ESTROGEN (E(2))-DEPENDENT OVIDUCT GLYCOPROTEIN IN THE BLASTOMERE MEMBRANE AND ZONA-PELLUCIDA AND IN ITS ASSOCIATION WITH F-ACTIN

The luminal environment of the estrogen (E(2))-dominated mammalian ovi duct generates and sustains the environment in which the first embryon ic cleavages take place. The objective of this study was to determine, by use of an antiserum against an E(2)-dependent sheep oviduct secret ory glycoprotein (M(r) 90 000-92 000), whether the E(2)-dominated and pregnant oviduct of the Djungarian hamster (Phodopus sungorus) release s an antigenically related protein. If the protein was present, a seco ndary objective was to define its fate and association with filamentou s-actin (f-actin) and chromatin patterns in early cleavage-stage embry os. Oviduct flushings containing embryos (1-cell fertilized, 2-, 4-, a nd 8-cells), and uterine flushings (> 16 cell embryos) were obtained f rom pregnant hamsters. Embryos were removed from flushings, and oviduc t secretions were analyzed by Western blotting. The zona pellucida was removed with acid Tyrode's solution from approximately half of the 2- , 4-, and 8-cell embryos. Zona-intact and zona-free embryos were then fixed and subjected to triple immunofluorescence staining with an anti serum to the sheep oviduct protein, rhodamine phalloidin, and Hoechst 33258. An antigenically related protein (M(r) 200 000) was detected in oviduct secretions of E(2)-treated, ovariectomized, and pregnant hams ters, and not in secretions from ovariectomized controls. In the zona pellucida of 1- and 2-cell embryos, the oviduct protein displayed an i ntertwining reticular organization that was replaced by a diffuse and more intense accumulation in 4-, 8-, and > 16-cell embryos. In 2-cell embryos, punctate foci of the oviduct protein were distributed unevenl y over the apical blastomere plasma membrane, forming patches in regio ns of f-actin exclusion, which were absent at later development stages . At the 4- and 8-cell stage of development, as blastomeres lost their spherical form by minimizing intercellular spaces, the oviduct protei n took on a polarized arrangement and was intensely concentrated on me mbrane areas involved in cell-cell contact that were also the focus of f-actin. These data show that in early cleavage-stage hamster embryos , the intensity and pattern of staining for an E(2)-dependent oviduct protein (M(r) 200 000) that is released into the oviduct lumen during embryo transport can be distinguished on the basis of membrane f-actin display and blastomere number and shape. These events may mediate cel lular processes related to blastomere cleavage, shaping, and/or adhesi on that occur in the oviduct.