Characterization and distribution of neutral and acidic mucins in the alimentary canal of an Indian freshwater major carp, Catla catla (Hamilton) by histochemical methods.

The distribution and chemical nature of acid and neutral mucins in the various regions of the alimentary canal of Catla catla (Ham.) have been studied. Both acid (sulfated and non-sulfated) and neutral mucins have been found to occur as a mosaic of complex substances in the different mucous cell types (secretory and non-secretory--both mature and immature) in the various regions of the alimentary canal (buccopharynx, oesophagus, intestine, and rectum). Acid mucin (both sulfated and non-sulfated) of the secretory and mature non-secretory mucous cells in the buccopharyngeal and oesophageal regions, however, predominates since these 2 regions are known to participate actively in food lubrication while the sulfated acid mucin keeps the internal mucosa moist. Mucous mother cells which originate from the multipotent progenitor cells contain exclusively neutral mucin in the form of neutral mucopolysaccharide granules. In the course of development these mucous mother cells are gradually pushed towards the periphery of the mucosa and transformed into mature and secretory mucous cells through an intermediate stage--the immature mucous cells. The latter cells during development synthesize intact acid mucopolysaccharide granules which ultimately fuse to produce a compact mass of mucin (both acid and neutral) in the mature and secretory mucous cells.