Uteroglobin in the rabbit. I. Intracellular localization in the oviduct, uterus, and preimplantation blastocyst.

The localization and release of uteroglobin (UGL) were investigated immunohistologically in the oviducts and uteri of female rabbits from oestrus through the 7th day post coitum and the blastocyst on the 7th day post coitum. UGL was detected within Fallopian tube cells even during oestrus. Granules of UGL appeared toward the bases of these cells. Subsequently, the cells became almost entirely filled with UGI. Drop-like protrusions of the apical cytoplasm suggest a mechanism of apocrine extrusion. All stages of filling and extrusion were visible during the entire preimplantation period. During oestrus, synthesis of UGL within uterine cells becomes sufficiently advanced so that extrusion has either already begun or is about to begin. UGL positive material first appears in the supranuclear regions. Later the entire cytoplasm shows a positive reaction. An uneven distribution of UGL cells is observed in the endometrium. Since only the glands adjacent to the myometrium and cells of the cavum epithelium contain UGL, a striking mosaic of UGL positive and negative cells results. The present report is the first detecting UGL in single cells of the blastocyst. Both entodermal and ectodermal cells proved to be UGL positive. The synthesis and section of UGL in the oviduct and uterus and the possible origins of UGL in the blastocyst are discussed.