Evidence for the regulation of glycosylation of golden hamster (Mesocricetus auratus) oviductin during the estrous cycle.

The oviduct contributes to the reproductive environment by secreting various factors, including a family of glycoproteins termed oviductins. Although many studies have demonstrated that ovarian hormones modulate oviductin gene expression in several mammalian species, there has been controversy surrounding the regulation of golden hamster oviductin. The current study was undertaken to investigate the transcriptional and translational modifications of hamster oviductin during the estrous cycle. First, we verified that hamster oviductin mRNA expression remains constant throughout the estrous cycle by semiquantitative reverse transcription polymerase chain reaction. We then developed a polyclonal antibody against recombinant hamster oviductin (rhaOvm). The anti-rhaOvm antibody was subsequently used in conjunction with quantitative immunocytochemistry to investigate the oviductin levels in the hamster oviduct during the estrous cycle. Quantification of immunolabeling revealed a high, consistent level of glycoprotein throughout the estrous cycle. Therefore, it appears that the production of oviductin is not regulated differentially during the estrous cycle. Size variations in hamster oviductin expression were also investigated by Western blot analysis. The oviduct contains several forms of oviductin at each stage of the estrous cycle, the native glycosylated form(s) of 160-350 kDa, and several precursor forms of 70-100 kDa. Although variations in the intensities of the polydispersed band were not evident during the estrous cycle, additional bands ranging from 90 to 100 kDa were detected in the estrus, metestrus, and diestrus 1 stages. The results from the present investigations suggest that whereas ovarian hormones do not appear to influence the hamster oviductin mRNA and protein expressions, glycosylation of hamster oviductin appears to be differentially regulated during the estrous cycle.