Early prenatal development of the brush border enzymes in the embryonal intestine.

Standard methods were used for the study of the activity of brush border enzymes in the epithelium of the intestine of 45 human embryos aged from 4 to 22 weeks of the intrauterine life. Enzymes of the peptidase group (DPP IV, APM, APA, GGT, BBEP), of the phosphatase group (ALP, ACP, AMP, ATP), and of the disaccharidase group (saccharose, lactase, trehalase) were studied. In the embryonal developmental period (to week 8), the activity of proteases was mainly detected on the luminal surface of the primitive pseudostratified columnar epithelium of the intestine anlage. The highest activity was displayed by DPP IV. In the period from the 8th week, villi are formed from the duodenum up to the ileum. After week 9, differentiation of Lieberkühn crypts was observed. The activity of proteases was very high (DPP IV especially) in the differentiating microvillous zone of primitive enterocytes. Gradient of apex-base activity of the villus was maximal on the apex of villi. After week 12 of the intrauterine life, the activity of disaccharidases ALP and AMP occurs in the differentiating brush border, and a low activity of BBEP of the protease group is present.