Histochemical localization of 5'-nucleotidase in the lymphatic endothelium.

Histochemical localization of 5′-nucleotidase (5′-Nase) in the lymphatic endothelium of rat stomach was studied by combined light and electron microscopy. Lymphatic capillaries and blood capillaries were distinguished histochemically on cryostat sections using 5′-Nase-alkaline phosphatase double staining.The distribution of lead-demonstrated 5′-Nase activity in the lymphatic capillaries could be determined by comparing the images of the same section as seen by light and backscattered imaging scanning electron microscopy. The specificity of the 5′-Nase reaction was obtained by inhibiting nonspecific alkaline phosphatase by including L-tetramisole in the incubation medium for 5′-Nase activity. The intensity and localization of 5′-Nase activity on the walls of lymphatic capillaries were also determined by the lead-based or cerium-based method. The intense reaction products of 5′-Nase activity were predominantly deposited on the outer surface of the plasma membrane of the lymphatic endothelial cells. The cerium-based method revealed fine and linear reaction products on the plasma membrane.