Influence of experimental bypass on cellular kinetics and maturation of small intestinal epithelium in the rat.

The effect of experimental bypass on the intestinal epithelium of the rat was investigated from 2 to 360 days after creating a Thiry-Vella fistula. Within 7 to 14 days the number of cells per villus column and, to a lesser degree, the number of cells per crypt column decreased and subsequently these values remained constant up to 1 year. Radioautography did not show any changes in the percentage of labelled cells per crypt column, after incorporation of [3H]thymidine. In addition, the relative size of the proliferative cell compartment in the crypt, the number of crypts per unit length of small intestine and the crypt-villus ratio remained unchanged. Scintillation counting of isolated crypts from the Thiry-Vella fistulas showed that the number of cells per crypt was markedly reduced. Scanning electron microscopy revealed that the three-dimensional size of the villi was also reduced. The activities of nonspecific esterases and neutral alpha-glucosidase remained unchanged in crypt cells and were above control values in villus cells. The development of these biochemical characteristics of the villus cells seems to be independent of the luminal contents. It was concluded that deprivation of food passage and gastric, pancreatic, and liver secretions from a small intestinal segment primarily causes a reduction in the number of cells per crypt, which leads to a lower cell production. In turn, this is responsible for the reduction of the functional villus cell compartment.