Factors influencing villus size in the small intestine of adult rats as revealed by transposition of intestinal segments

Abstract

As an index of villus size, the number of epithelial cells per representative villus section was counted in longitudinal sections of the rat small intestine. Villus size was found to decrease gradually along the length of the small intestine, with villi being nearly three times as large in upper duodenum as in terminal ileum. The influence of various surgical operations on villus size was then examined. In ileal segments inserted into the jejunum, villi enlarged to the size of local jejunal villi. In jejunal segments inserted into the ileum, villi decreased almost to the size of local ileal villi. Thus, villus size was influenced by the environment, that is, most probably by the different types of chyme in jejunum and ileum.In duodenal segments inserted into the ileum, villi did not decrease in size, and distally located ileal villi enlarged. This and other experiments indicated that the duodenum produced secretions which not only neutralized the villus-reducing effect of the ileal environment, but also exerted a potent villus-enlarging effect. Pyloric secretions had a similar villus-enlarging effect.Segments of intestine were made into blind sacs by closing their proximal end and joining their distal end to the colon, so as to remove the influence of the chyme. Villus size decreased in sacs of jejunum and lower duodenum (without the duodenal papilla), but increased in sacs of ileum. Thus in the three types of sacs, there was a tendency for villi to acquire an intermediate size.In conclusion, a n intermediate villus size, which is postulated to exist in chyme-free, non-functional intestine, would normally be modified by two types of factors: villusenlarging factors present mainly in pyloric and duodenal secretions, and villus-reducing factors present in the ileal chyme. Interaction between these factors would result in the gradient of villus size along the small intestine.In the small intestine of the rat, villi exhibit a gradual decrease in size from the upper duodenum to the terminal ileum, as may be seen in figures 1-5 (Altmann and Enesco, '67). Since villi have a rapidly renewing component, the epithelium, the constancy of their pattern must be maintained in each region by proper regulatory mechanisms. The aim of the present work was to find out what type of factors were involved in the mechanisms controlling villus size and, in particular, whether these factors were intrinsic to the tissue or provided by the environment. The approach used was to separate intestinal segments by surgical procedures and to transpose them to other gastro-intestinal areas. In some cases, the segments were inserted in different locations, but within the intestinal continuity; the villi were thus exposed to a different intestinal content, since the content varies from fluid gastric chyme in the duodenum to semisolid fecal material in AM. J. ANAT., 127: 15-36. the terminal ileum. In other cases, segments were made to open as blind sacs onto the side of ileum or colon, thus becoming largely non-functional as well as empty of ...

The relationship between intestinal histology and function as shown by compensatory enlargement of remnant villi after midgut resection in chickens

“…Although in the rat the villus number increased after intestinal resection (Bochkov, 1959), intestinal villi of chickens tested in this study adapt to activated intestinal absorptive function not by increasing their numbers but by fusing together into larger villi. In rats, in addition to villus hyperplasia after transposition of the ileum to the jejunal location (Dowling and Booth, 1967;Altmann and Leblond, 1970;Wang et al, 1998), hypertrophy of microvilli and lateral cell membranes was also reported after midgut resection (Tilson and Wright, 1971a,b).…”

“…Similarly, intestinal villi in intact chickens gradually decrease in length (Rolls et al, 1978) and size (Altmann and Leblond, 1970) moving from the duodenum to the ileum. Lower villus height (Khambualai et al, 2009) and narrower cell area (Incharoen and Yamauchi, 2009) were observed in the ileum compared with the jejunum.…”

Effect of Chronic Pancreatic Juice Diversion on Enteroglucagon Secretion and Intestinal Mucosal Growth in Dogs.

“…Altmann investigated the effects of luminal pancreatic juice and bile on the growth of small intestinal mucosa in rats; it was reported that pancreatic juice and bile had trophic effect on the intestinal mucosa (Altmann and Leblond 1970;Altmann 1972). In their model, a duodenal segment including the pancreatic duct was anastomosed to the ileum.…”

“…pancreatic juice diversion; enteroglucagon; intestinal mucosal growth; pancreaticoileostomy It was previously reported that intestinal pancreatic juice plays an important role in intestinal adaptation (bowling 1982), and that pancreatic juice has a trophic effect on the small intestinal mucosa (Altmann and Leblond 1970;Altmann 1972). However, others have suggested that it is still controversial whether pancreatic juice has a trophic effect on intestinal mucosa (Miazza et al 1982).…”

The Trophic Effects of Long Chain Triglycerides on the Atrophic Ileal Mucosa of Rats.

“…These findings suggest that the proliferative effects of fat are not associated with the adequacy of the energy supply. Orally administered fat is known to increase exocrine pancreaticc juice and bile (12) and to promote the release of neurotensin (13,14). These mechanisms may be related to the trophic effects of the 4% FED on the intestine (15).…”