Expression and localization of cyclooxygenases in the oviduct of laying hens during the ovulatory cycle

Abstract

Prostaglandins (PGs) play important roles in regulation of the functions of the hen oviduct. However, little is known about the expression and localization of the rate-limiting cyclooxygenases (COX-1 and COX-2) in the oviduct. The aim of this study was to determine the COXs expression and localization in the different segments of the oviduct and to investigate changes in their expression levels during the ovulatory cycle of laying hens. White Leghorn laying hens were killed at 0, 4, 7, 16 and 24 h after oviposition, and samples from the infundibulum, magnum, isthmus, uterus, and vagina were collected. Gene and protein expressions were examined by real-time PCR and western blot, respectively, for both COX-1 and COX-2. Localization of COX-1 and COX-2 in the hen oviduct was determined by immunohistochemistry and PCR analysis of samples collected by laser capture microdissection (LCM). The expression level of COX-1 was highest in the infundibulum, while that of COX-2 was significantly higher in the uterus than in the other segments. The expression levels of COX-1 in the infundibulum and COX-2 in the uterus were higher at 0 and 24 h after oviposition, just prior to subsequent ovulation and oviposition. Western blot analysis confirmed the presence of COX-1 and COX-2 in all oviductal segments. The density of COX-2 was the highest in the uterus, and did not change during the ovulatory cycle. COX-1 and COX-2 were localized in the surface epithelium of all oviductal segments besides the uterine tubular glands. We conclude that both COXs are differentially expressed in the different oviductal segments with a temporal association to ovulation and oviposition. COX-1 and COX-2 may play an important role in the infundibulum and uterus, respectively, and COX-2 may be one of the factors regulating the induction of oviposition.

Keywords: Cyclooxygenases; Laying hen; Oviduct; Prostaglandins.