Cellular expression of the gut chitinase in the stomach of frogs Xenopus laevis and Rana catesbeiana

Abstract

Gut chitinase, originally identified as acidic mammalian chitinase, is secreted from the salivary gland and stomach in humans and mice, but exclusively from the liver in cattle. Since the organs producing gut chitinase differ depending on the species, here we determined the expression site of this enzyme in the gastrointestinal tract of frogs, Xenopus laevis and Rana catesbeiana, which eat a large amount of chitin-coated animals, using in situ hybridization and immunohistochemistry. The chitinase was detected only in the oxynticopeptic cells of gastric glands and was accumulated in secretory granules in the cytoplasm, suggesting that the enzyme may be released into the gastric lumen directly. In addition, the enzyme was not found in the stomach of larvae, but was detected at stage 62 of metamorphosis and later, when the frogs changed from a herbivorous to a carnivorous diet.