Ultrastructural evidence that specialized regions of the murine oviduct contribute a glycoprotein to the extracellular matrix of mouse oocytes.

Previous studies have identified a glycoprotein (GP215) that is secreted by the murine oviductal epithelium and subsequently becomes sequestered within the perivitelline space of oocytes and developing embryos (Kapur and Johnson, Dev. Biol. 112:89-93, 1985; J. Exp. Zool. 238:249-260, 1986). The ultrastructural localizations of GP215 in the perivitelline space of ovulated oocytes and in the oviductal epithelium are described here. The glycoprotein is shown to be associated with a morphologically discrete extracellular matrix that provides a unique microenvironment for fertilization and early developmental events. In addition, putative secretory granules that contain this glycoprotein are observed in specific segments of the murine oviductal epthelium, suggesting regional differences in the composition of oviductal secretions.