Differentiation of epithelial cells in human jejunum: localization and quantification of aminopeptidase, alkaline phosphatase and aldolase isozymes in tissue sections.

Sections from human jejunum were stained histochemically for aminopeptidase and alkaline phosphatase and the aldolase isozymes were detected with the mixed aggregation immuno-cytochemical technique. All enzyme concentrations increased from the bottom to the upper part of the crypt. The concentration of aldolase-A per cell was the same in the upper part of the crypt and the villus, whereas the concentration of the other three enzymes was still higher. Therefore, high amounts of aldolase-B, aminopeptidase and alkaline phosphatase are present in cells highly active in absorption in a fashion similar to that found in the proximal tubule cells of kidney. The relatively undifferentiated cells of the crypts contained both aldolase-A and aldolase-B. Alkaline phosphatase gains its full activity later than aminopeptidase. The synthesis of microvillar membrane enzymes comes to an end earlier than that of the cytosol enzymes.