The Distribution and Architecture of Lymphatic Vessels in the Rat Stomach as Revealed by an Enzyme-Histochemical Method

Enzyme-histochemical methods of staining for 5'-nucleotidase (5'-Nase) and alkaline phosphatase (ALPase) were successfully applied to study the distribution and architecture of lymphatic vessels and their relationships to blood vessels in the rat stomach. Extensively lymphatic capillary networks were found in the gastric wall, but there were significant differences in their extent, pattern, distribution and structure in the four different zones: esophagus-stomach (E-S), forestomach-corpus (F-C), corpus-antrum (C-A) and antrum-duodenum (A-D). 5'-Nase-ALPase double staining revealed that the 5'-Nase-positive lymphatic vessels run in close proximity to ALPase-positive arteries and veins. The fine blood capillary network was located superficially to the lymphatic network within the same layer in the gastric wall. The abundant lymphatic network located in the deep lamina propria and the lamina muscularis mucosa was always closely associated with the base of the lowest gastric glands, and yet no interglandular lymphatic capillaries were encountered in the corpus or antrum. In contrast, fewer lymphatic capillaries were present in the lamina propria beneath the squamous epithelium of the forestomach. The distribution of the well-developed lymphatic networks with valve-like structures in the submucosa and subserosa exhibited typical features, i.e., the distribution was annular in the submucosa and fan-shaped in the subserosa in the antrum near the duodenum. Open junctions of lymphatic endothelial cells were seen in the deep lamina propria and submucosa. Collecting lymphatics containing valves were mainly located deep in the submucosa and subserosa. The deep lamina propria and submucosa may play a key role in lymph formation and interstitial tissue fluid homeostasis as well as in pathological processes in certain diseases. The present findings obtained by interstitially injecting ultra-fine carbon particle suspensions or Evans blue showed that a great deal of lymph drained into the lymphatics accompanying the left gastric artery. The existence of a forestomach may explain the complicated organization and constitution of lymphatic networks in the rat stomach.