Enzyme patterns and protein absorption in rat colon during development.

Four enzymes were studied in the rat colon during perinatal development, namely, carbonic anhydrase, beta-D-galactosidase, and alkaline and acid pphosphatase. Quantitative analyses of tissue extracts revealed a peak in carbonic anhydrase activity 10 days after birth and histochemically most of the enzyme was found at the surface of the colonic mucosa. A similar localization was found for beta-D-galactosidase, which displayed a peak of activity in the 1-day-old rats. Alkaline phosphatase activity reached its maximum 5 days after birth, and by electron-microscopical histochemistry this enzyme was traced to the microvillous border, supranuclear vesicles and tubules, meconium bodies and the lateral surfaces of the principal cells. Acid hosphatase activity was also found in the microvillous border, in the supranuclear vacuoles and meconium bodies and in the Golgi apparatus. In the infant rat colon all these enzymes had higher activities and sometimes a different localization than in the adult rat, which indicates functional differences between the young and the adult animals. An example is the absorption of proteins. Peroxidase and insulin, given as enemas, were absorbed in the infant rat colon, but this capacity was much reduced after weaning.