CHARACTERIZATION OF ISOLATED DUODENAL EPITHELIAL-CELLS ALONG A CRYPT-VILLUS AXIS IN RATS FED DIETS WITH DIFFERENT IRON CONTENT

The intestinal mucosa is characterized by cell proliferation, commitme nt, differentiation, digestion and absorption. These processes occur a t specified locations along the crypt to villus axis. A technique is r eported for the isolation of cells along this axis which allows the st udy of any one of these processes in an enriched population of cells. As an example, the uptake of transferrin-bound iron by enterocytes was studied. Rats were fed diets normal, high (3% carbonyl iron) or low i n iron for 12 days. Cells from either the duodenum or ileum were isola ted by incubating in a Ca2+-, Mg2+-free, cation chelating solution for varying periods. The incorporation of thymidine into DNA was measured in these cells as a marker of the crypt region, while alkaline phosph atase and sucrase activities marked mature enterocytes. The in vivo up take of transferrin-bound Fe-59 was measured in cells isolated either 2 or 4 h after intravenous injection. This procedure resulted in the i solation of 10 fractions of viable cells. Earlier fractions were enric hed at least 10-fold in villus cells and the last fractions in crypt c ells. Cells in intermediate fractions were at various stages of develo pment. Uptake of transferrin-bound iron into enterocytes was highest w ith feeding an iron-loaded diet compared with control or iron-deficien t diets. However, with all diets uptake was highest in crypt cells and this fell at the crypt-villus junction to be only 25%, as high at the villus tip as the crypt. A technique for the reproducible isolation o f viable enterocytes along a crypt-villus axis is described. Transferr in receptor activity changes with maturation of the enterocyte.