| Summary: | Mucosal barrier system formed by mucus layer, epithelial cell junctional structures, and leukocyte activity, play important role to prevent infection by microbes in mucosal tissue. Previous study reported that expression of mucin and tight junction-related molecules are changed during the molting phase compared with that in the laying phase. It is unique that many of the functions of oviduct are regulated by gonadal steroids, namely estrogen and progesterone. The aim of this study was to aprove of the effects of estrogen and progesterone on the expression of mucin and tight junction molecule claudins in the lower oviductal segments in hens.White Leghorn laying and molting hens were used. A proportion of the molting hens (n = 5 in each group) were injected with sesame oil (control), estrogen or progesterone. The lower segments of oviduct (isthmus, uterus, and vagina) of these birds were collected. Gene expression of mucin and claudin-1, -3, -5 was analyzed by quantitative reverse transcriptase polymerase chain reaction (RT-PCR). Localization of mucin5AC and claudin-1 protein was examined by immunohistochemistry. Localization of mucin polysaccharide was performed by alcian blue (AB) staining. In the lower oviductal segments, expression of mucin and claudin-1, -3, and -5 genes were up-regulated by both estrogen and progesterone. Immunoreactive mucin5AC and claudin-1 protein, as well as AB-positive mucopolysaccharidewasincreased by those gonadal steroids. These results suggest that gonadal steroids, estrogen and progesterone, may play a role to regulate mucosal barrier formed by mucin and tight junction molecule claudins at the lower oviductal segments. This mucosal barrier system in the oviduct is expected to play important roles to protect the oviductal tissues from infection by pathogenic microorganisms.
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