Histochemistry of the human duodenal mucosa with special reference to the gradient of activities of the brush border enzymes.

Histochemical examination of aspiration biopsy specimens of the duodenum in 8 healthy volunteers and 23 patients with various gastrointestinal disorders revealed no characteristic abnormality except for a rather frequent absence of the activity of disacharidases especially of lactase. A distinct difference of disacharidase was established between the duodenum and the jejunum in some individuals. A systematic study of different levels of the upper gastrointestinal tract established the fact that the activity of brush border enzymes of enterocytes starts to appear in individually different parts of the duodenum and sometimes even as low as in the jejunum. The distribution of lysosomal enzymes and the activity of dehydrogenases display differences as well. Consequently specimens from different parts of the duodenal and jejunal mucosa are not equivalent and cannot be used alternatively for diagnostic purposes. Biopsies of duodenal mucosa are not adequate for the diagnosis of the malabsorption syndrome.