Differences in the mucosal surface barrier formed by mucin in the lower oviductal segments between laying and molting hens.

The aim of this study was to determine the differences in the mucin expression that forms a mucosal surface barrier in the oviduct between laying and molting hens. The lower segments of oviducts (isthmus, uterus, and vagina) of White Leghorn laying and molting hens were collected. Localization and gene expression of mucosal mucin were analyzed by quantitative reverse-transcription PCR of mucin mRNA and mucin5AC immunohistochemistry. Sugar residues were localized by lectin (WGA or Jacalin) histochemistry. Expression of mucin mRNA was significantly declined in the lower oviductal segments in molting compared with laying hens. Immunoreactive-mucin5AC was localized in the mucosal epithelium and on the epithelial surface of laying hens, whereas it was reduced in molting hens. Substances positively stained by WGA and Jacalin were identified on the surface of the mucosal epithelium in the lower oviductal segments in laying and molting hens. These results suggest that mucin synthesis in the lower segments of the oviduct is reduced, although the existence of WGA- and Jacalin-positive sugars may be kept even in the molting phase. The reduction of mucin synthesis may result in a decline of mucosal barrier function in the molting phase.