Oviduct acid mucus glycoproteins in the estrous rabbit: ultrastructure and histochemistry

Epithelial glycoproteins are likely to be important in many aspects of reproduction. The rabbit oviduct produces mucus glycoproteins. This is indicated both by histochemistry and by gelation of a mucus coat around the rabbit ovum during its tubal transport. We report here that the production of highly acid mucus glycoprotein (apparently of the type that coast the ovum) is confined to the isthmus and, to a lesser extent, the mucosal crypts of the ampullary-isthmic junction; the ampulla is not involved. Using a method of perfusion-fixation that includes the polycation alcian blue in conjunction with glutaraldehyde to precipitate and stabilize glycoproteins, we have demonstrated that this mucus, at least in rabbits in estrus, occupies the isthmic lumen but not the ampullary lumen. Histochemistry shows that it is the electron-lucent secretory granules of the isthmus and ampullary-isthmic junction, but not the denser granules of the ampulla, that exhibit staining characteristics of highly-acid mucus glycoproteins. Important opportunities are likely to exist for interaction of this isthmic mucus with spermatozoa and with fertilized ova during their isthmic transport.