Demonstration of the Rat Lymphatic Vessels Using Immuohistochemistry and In Situ Hybridization for 5'-Nucleotidase

The cellular distribution of 5'-nucleotidase (5'-Nase) was studied in the rat tissues at the levels of protein and mRNA by use of immunohistochemistry and in situ hybridization, and compared with that of reaction productsby enzyme-histochemistry. 5'-Nase activity, immunoreactivity of ecto-5'-Nase (CD73) and hybridization signals for its mRNA were colocalized in the lymphatic vessels including central lacteals of the small intestine, suggesting that 5'-Nase is actually produced in the lymphatic endothelial cells and allocated to their cell membrane as an enzyme to regulate lymph production and flow. Double immunostainig for CD73 and Factor VIII-related antigen clearly showed the distinction and relationship between lymphatics and the blood vessels. The present findings support our view that 5'-Nase is an available marker of lymphatics, and indicate the usefulness of the histochemical methods for 5'-Nase not only for demonstration of lymphatics, but also for examination of the functional roles and dynamics of 5'-Nase in the lymphatic endothelial cells in physiological and pathological conditions.