Adult male rats were fasted for 0 (controls), three, five and seven days; a group was refed for one day after six days of starvation. Histological samples were taken from five regions along the length of the small intestine. The sizes of the villi, crypts and mitotic pool were estimated by measuring the number of epithelial cells per villus and crypt section and the number of mitotic figures per crypt section. Additional studies were carried out using colchicine for estimating mitotic time and methotrexate for inhibiting mitosis.All three parameters decreased progressively during starvation; the decrease in villus size was most pronounced in the duodenum and gradually less distalward. Refeeding increased the mitotic pool in every region; crypt size did not increase and villus size increased slightly in duodenum and jejunum only. When refeeding was combined with mitotic inhibition, the cell population of the crypts became depleted by 3 0 4 0 % without change in villus size; thus, renewal appeared to continue by crypt cells migrating to the villi.Mitosis in the crypts is used for epithelial renewal in the adult intestine. The calculated turnover time of the epithelium was longer than normal and similar in every stage of starvation. Refeeding appeared to stimulate renewal. Since villus size changed somewhat independently from mitotic activity, the involvement of a separate mechanism controlling villus size was indicated.Mucosal size is determined mainly by the size of the crypts and the villi in the small intestine. The size of these structures and the size of the mitotic pool in the crypts were measured in the present work in starved and refed rats.In accordance with previous works (Altmann, '67; Altmann and Leblond, '70; Altmann, '71), the number of epithelial cells present in the villi and the crypts was used as an index of villus size and crypt size, respectively. These indices combined with the data on mitosis provided some information on the rate of epithelial renewal.The same previous works have provided evidence that various intestinal secretions present in the intestinal chyme influence villus size, crypt size and, to a certain extent, epithelial renewal. The purpose of the present work was to extend these studies to the investigation of the effects of food.AM. J. ANAT., 133: 391-400.
MATERIALS AND METHODSAnimal techniques. Adult male Wistar rats weighing about 310 gm were used. Groups of five animals were fasted for 0 (controls), three, five and seven days. Water was freely available. A group of five rats was fasted for six days and then refed with Purina Laboratory Chow for one day. Another group of three rats was refed similarly but with powdered Purina Laboratory Chow which contained 0.25 mg methotrexate per gm. Finally, each of six additional animals were injected subcutaneously with 0.3 mg of colchicine three hours before sacrifice; three of these animals were maintained on normal diet and three of them were fasted for seven days prior to sacrifice.The animals were killed between 9 AM and 11 A...
