Distribution of glucose-6-phosphatase and 5-nucleotidase in the digestive system of two teleost fishes.

The distribution and histochemical localization of G6Pase and 5-nucleotidase in the different parts of the alimentary canal of two teleost fishes, Heteropneustes fossilis and Barbus sophore have been studied. The major sites of activity of the two enzymes are intestinal mucosa and liver. G6Pase is localized in the cytoplasm of the absorptive cells of the intestinal mucosa while 5-nucleotidase is present in the cytoplasm as well as nucleus and cell membrane. In the intestine, the anterior portion shows more stronger activity than in the middle and posterior portions. Mild activity is also noticed in the mucosa and gastric glands of the stomach. G6Pase activity is stronger than 5-nucleotidase activity in all the portions. Weak 5-nucleotidase activity is found in the submucosal connective tissue and the nuclei of the intestine. The goblet cells, muscularis abd serosa are negative in all the portions. G6Pase activity is stronger in the herbivorous fish Barbus sophore than in the omnivorous form Heteropneustes fossilis. In the liver, stronger activity of two enzymes is localized in the hepatocytes surrounding the sinusoids. Connective tissue and endothelial lining are negative.