Cytochemical features of the digestive tract mucosa of Hemisorubim platyrhynchos (Siluriformes: Pimelodidae).

Membranous organelles, acid glycoconjugates and lipids were characterized in the digestive tract mucosa of Hemisorubim platyrhynchos by cytochemistry techniques. Two types of mucous-secreting cells were observed in the digestive tract epithelium: goblet cells in the oesophagus and intestine and epithelial cells in the stomach. These cells had a Golgi apparatus more developed than the other cell types. The cytochemical analysis revealed that secretory granules are reactive to acid glycoconjugates, varying in reaction intensity according to the region of the digestive tract. Acid glycoconjugate reactions were also observed in oesophageal epithelial cell microridges and in enterocyte microvilli. In the digestive tract, acid glycoconjugates act to protect the epithelial surface, increasing mucous viscosity, which facilitates the passage of food, prevents the binding of parasites and facilitates their removal. Through lipid staining, a coated membrane was observed around each secretory granule of the oesophageal and intestinal goblet cells, while gastric epithelial cells granules were fully reactive. Oxynticopeptic cells of the gastric glands showed lipid droplets in the cytoplasm and also in the mitochondrial matrix, which act as an energy reserve for these cells that have a high energy demand. Enterocytes showed a well-developed smooth endoplasmic reticulum, especially in the apical region of the cell, being related to absorption and resynthesis of lipids.