The effects of glutamine on intestinal epithelial cell proliferation in parenterally fed rats

Abstract

Background: Several papers have indicated that glutamine is a preferred fuel for the enterocyte and that it can increase intestinal epithelial cell proliferation.

Aims: To investigate the effects of glutamine on intestinal epithelial cell proliferation in the parenterally fed rat.

Methods: Five groups of six rats were fed parenterally; a group of orally fed rats was also studied. Crypt cell proliferation was studied after six days using native mitoses in microdissected crypts and bromodeoxyuridine labelling.

Results: No effect of treatment was seen on intestinal weight; however, the weights of the small intestine, caecum, and colon were all significantly heavier in the orally fed group than in the total parenteral nutrition groups (p<0.001). There was no effect of any of the glutamine treatments on mitotic activity in the small intestine. In the colon there was a small increase in native mitoses with glutamine (p=0.03). There was also an indication of increased proliferative activity in the first fifth of the small intestine and colon with glutamine. Little effect of glutamine on bromodeoxyuridine labelling in either site was observed, but there was a small but significant reduction in growth fraction of the colon of the glutamine treated group. The labelling distribution curve from sections and the mitotic distribution curve obtained from crypt squashes showed a good correlation.

Conclusion: Glutamine has a small, but significant effect on mitotic activity but only in the colon. Modest effects on the distribution of labelled cells were also seen.

Figure 1

The weights of the stomach (A), small intestine (B), caecum (C), and colon (D), expressed as a percentage of total body weight. ***p<0.001 versus TPN + alanine.

Figure 2

Native mitoses counts in crypt squash preparations in the small intestine and colon: (A) 50% small intestine; (B) 10% colon; (C) 50% colon; (D) 90% colon. **p<0.01, ***p<0.001 versus TPN + alanine.

Figure 3

Data from sections reformatted to express the proportion of labelled cells within five equal zones of the crypt and the distribution of mitotic figures scored by superimposing a grid over the individual microdissected crypts for the small intestine. The top shows the mean number of labelled cells or mitoses per zone. The bottom shows the proportion of labelled cells or mitoses in the zones. *p<0.05, **p<0.01 versus TPN + alanine.

Figure 4

Data from sections reformatted to express the proportion of labelled cells within five equal zones of the crypt and the distribution of mitotic figures scored by superimposing a grid over the individual microdissected crypts for the colon. The top shows the mean number of labelled cells or mitoses per zone. The bottom shows the proportion of labelled cells or mitoses in the zones. *p<0.05, **p<0.01 versus TPN + alanine.