CRYPT AND VILLOUS EPITHELIAL-CELLS IN ADULT-RAT SMALL-INTESTINE - NUMERICAL AND VOLUMETRIC VARIATION ALONG LONGITUDINAL AND VERTICAL AXES

Previous studies on the small intestines of certain adult rodents have suggested that the total number of crypt epithelial cells is equal to the number of villous epithelial cells. This possibility is examined on adult male Sprague-Dawley rats using design-based stereological met hods. Small intestines were removed and divided into four segments of equal length. For each segment, numbers and mean volumes of epithelial cells in crypts and villi were estimated and then combined to give va lues for the entire intestine. Variations along the vertical (crypt-vi llus) axis and the intestinal long (pyloro-ileocaecal) axis were exami ned. Cell numbers in crypts and on villi varied from segment to segmen t. Villus:crypt cell ratios proximally were roughly double those found distally. The ratio for the entire intestine was, on average, 1:6 vil lous cells per crypt cell. These results demonstrate that numbers of c rypt and villous cells need not be equivalent. Previous findings may r eflect the fact that ratios fluctuate according to circumstances (e.g. , with species, age, nutritional status, disease, etc) or may be due t o technical differences in tissue sampling and morphometry. Cell volum es varied along the crypt-villus axis as well as between segments, con firming known gradients of maturation and activity. Finally, the size of the intestinal epithelial proliferon was calculated in terms of the average numbers of epithelial cells per villus and of crypt epithelia l cells feeding on to it.