Differential Distribution of Digestive Enzymes in Isolated Epithelial Cells from Developing Human Fetal Small Intestine and Colon

The human fetal colon has morphological and biochemical characteristics similar to that of the small intestine during development. A comparative study of these two organs was undertaken by selectively isolating their respective epithelium at different ages of gestation. Histological and biochemical analysis revealed a complete and selective removal of the epithelium from the underlying tissue regardless of their stage of development. Intestinal and colonic epithelial cells showed substantial differences with respect to protein content and distribution. All brush border membrane enzymes studied were present in the colon, although in much lower quantities than in the corresponding intestine. Between 90 and 99% of total disaccharidases, glucoamylase and gamma-glutamyl transpeptidase activities were recovered in the isolated cells. Epithelial content and distribution of alkaline phosphatase (ALP) activity differed markedly, however, between these two tissues. More than 45% of intestinal ALP activity was of nonepithelial origin at 15 weeks, and this percentage increased in a craniocaudal fashion to reach greater than 93% in the 18-week-old colon. Inhibition studies using phenylalanine and levamisole showed that these intestinal and colonic isoenzymes are similar in nature although they differ in their respective distribution. The use of pure fractions of epithelial cells provides an ideal system in which to compare specifically the functional development of intestinal and colonic epithelium.