Immunohistochemical localization of oviductin in the endometrial lining of the golden hamster (Mesocricetus auratus) during the estrous cycle and early gestation

Oviductal non-ciliated secretory epithelial cells, under hormonal stimulation, synthesize and secrete a family of glycoproteins referred to as oviductins. These glycoproteins are found in oviductal fluid in several mammalian species, and have been localized in the oviduct, and in the zona pellucida of ovulated oocytes. In the golden hamster, this glycoprotein is named hamster oviductin-I. Recently, an immunofluorescent study on hamster uterine tissue has revealed the presence of the glycoprotein in luminal epithelial cells in a heterogeneous labelling pattern during the estrous cycle. The mechanism of endometrial epithelial cell receptivity to hamster oviductin-1 is not known. In this study, immunohistochemical studies were performed using a monoclonal antibody against the oviductin in conjunction with silver enhancement technique, in an attempt to determine further the factors playing a role in uterine receptivity to oviductin-1. Paraffin sections of hamster uterus obtained from different stages of the estrous cycle and from days 1-6 of gestation, and paraffin sections of hamster oviduct obtained from days 1-6 of gestation were used in this study. The results we obtained using the silver enhancement technique show that hamster uterus luminal epithelial cells exhibit a homogeneous, high intensity immunolabelling pattern throughout the estrous cycle, whereas, during gestation, labelling intensity decreases as the period for blastocyst implantation approaches. Oviduct epithelial cells revealed no definite fluctuating pattern in immunolabelling intensities during gestation, indicating no change in synthesis and secretion of the glycoprotein during this period. It is speculated that receptors for hamster oviductin-1 are present at the apical cell surface of endometrial cells and that implantation of the developing blastocyst into the uterine wall is possible only following downregulation of these receptors. The use of the silver enhancement technique proves to be an effective tool in immunohistochemical studies at the light microscope level, as seen through this study.