Regulatory mechanisms for the expressions of local factors controlling bovine oviductal smooth muscle motility

Oviductal motility is required for transport of oocyte and embryo resulting in successful fertilization and implantation in mammals. The oviduct consists of epithelial, stromal and smooth muscle layers. Oviductal motility is systemically and locally regulated by various factors including prostaglandin F2 alpha (PGF) and endothelins (EDNs), and relaxing factors including prostaglandin E2 (PGE2) and nitric oxide (NO). The objective of our research is to clarify the regulatory system of oviductal motility including the production mechanisms of these factors in cattle. First, the expressions of regulating factors of oviductal motility were examined throughout the estrous cycle in the bovine oviduct. Some of them showed cyclical changes, which suggested that they were controlled by some other factors. Second, the effects of ovarian steroids or oviductal local factors on the expressions of PGs, EDNs and NO synthases were investigated using cell culture method. Several factors such as estradiol‒17beta, progesterone and lysophosphatidic acid affected the expressions of regulating factors of smooth muscle motility. In addition, we found that these actions differed between the ampulla and isthmus in same types of cultured cell. Our studies suggest that regulatory factors of oviductal motility are produced during the optimal period and at proper location to transport the oocyte and early embryo in the bovine oviduct. Although the precise control of oviductal motility is essential for successful pregnancy, methods for diagnosing and treating of its functional abnormality have not been established yet not only in cows but also in other animals including human. Our studies should contribute to improving the fertility rates in mammals