Migration and turnover of entero‐endocrine and caveolated cells in the epithelium of the descending colon, as shown by radioautography after continuous infusion of ³H‐thymidine into mice

Abstract

Adult male mice were given a continuous infusion of about 0.5 muCi of 3H-thymidine per gram body weight per day for periods varying from 1 to 60 days. Semithin sections of descending colon were cut from/plastic-embedded blocks and stained by a method combining silver impregnation and iron hematoxylin, by which argentaffin entero-endocrine cells and caveolated cells could be identified. From radioautographs, the labeling index of these cells was determined. One to three days after the beginning of 3H-thymidine infusion, label is observed in some of the stained entero-endocrine cells in the bottom of the crypts; the apices of these cells reach the crypt lumen and are joined to neighboring cells by terminal bars (junctional complexes). After five to seven days, labeled entero-endocrine cells are seen on the sides of the crypts, where their base stretches along the basement membrane and their apex has lost its terminal bar connections to neighboring cells. Finally, by 13 and 24 days, labeled cells are observed within the epithelium at the mucosal surface. The turnover time, which is taken to be equal to the mean time required for migration from site of origin to site of loss on the mucosal surface, has been estimated at 23.3 days. This is much longer than the 4.6 days required by the two main cell types of the epithelium -- vacuolated-columnar and mucous cells -- to travel the same route. It is likely that, after entero-endocrine cells lose their terminal bar attachment to other epithelial cells, they migrate independently and very slowly. Labeled caveolated cells are first seen in the crypt bottom one day after the beginning of 3H-thymidine infusion. By three to five days, they are on the sides of the crypts; their base is stretched along the basement membrane, but their apex retains its attachment to neighboring cells by terminal bars. By seven days, labeled caveolated cells are on the mucosal surface. Their turnover time has been assessed at 8.2 days. This is, again, longer than for the two main types to which they are bound by terminal bars throughout migration. The discrepancy is explained by the caveolated cells arising deeper in the crypts than most vacuolated-columnar and mucous cells.

The histochemical differences of intestinal gland epithelia in the rat colon with special reference to their glycoconjugates.

“…By various histochemical staining methods and radioautographic techniques, sialomucin was found in the goblet cell locating at the lower crypt of the proximal colon, and sulfomucin was contained in the same cell existing at the crypt of the near luminal surface of the proximal colon and throughout the crypt of the distal colon at the light microscopic level (4, 11-13, 25, 29, 30). However, at the electron microscopic level, it was reported that the mucigen granules of goblet cell and the vesicles of vacuolated cell contained neutral and acidic mucin by means of the dialyzed iron staining, colloidal thorium staining and radioautographic techniques (4,6,34,35). The composition of goblet cell mucins varied according to their level in the crypt as well as the different portions in the colon.…”

“…It is generally believed that the colonic glandular epithelia proliferate at the bottom of the crypt and they migrate upwards to the luminal surface (8,9,15,34). Then it is said that the secretory potentiality of goblet cells increases as those cell migrate from the bottom of the crypt to the surface of mucosa (21).…”

“…The colonic mucosal epithelia of the rat were composed of the columnar cell, goblet cell, vacuolated cell (8,15,19,24,34), caveolated cell (27,34) and various types of endocrine cells. On the mucosubstances covering those epithelial surface, it was shown that the mucin contained neutral-, sialo-and sulfoglycoconjugates.…”

“…The depth of the distal colon is deeper than that of the proximal colon. Although vacuolated cells exist in the distal colon, none are discernible in the proximals (9,34).…”

Cellular kinetics of gastrointestinal mucosa, with special reference to gut endocrine cells.

“…In the series of their studies (CHANG and LEBLOND, 1971;CHANG and NADLER, 1975;TsuBOUCHI and LEBLOND, 1979), it was described that vacuolated-columnar cells and mucus cells were found to be capable of mitosis in the mid or lower crypts, to migrate upwards and be lost from the mucosal surface within a life span of about 4.6 days. CELLULAR KINETICS OF GUT ENDOCRINE CELLS…”