Intracellular digestion of horseradish peroxidase by the intestinal cells of teleost larvae and juveniles.

The intracellular digestion of proteins by the rectal epithelium cells in larave and juveniles of five teleost species was investigated using horseradish peroxidase (HRP) as a marker substance. The HRP injected into the intestinal lumen was ingested from the apical surface of the cells, and was transported to the supranuclear area and then accumulated in several large granules. The supranuclear granules then changed to a number of small granules decreasing their HRP activity. The HRP activity finally disappeared from the small granules. The time required for complete digestion of HRP by the cells differed with species, 7 to 15 days in Oncorhynchus masou and 10 hours to one day in Hypomesus olidus. In H. olidus, stomachless larvae showed a higher ability of intracellular digestion than juveniles in which the gastric glands have already been developed.