Glutamine supplementation does not prevent small bowel mucosal atrophy after total parenteral nutrition in the rat

Glutamine supplementation to non-lipid parenteral nutrition has been demonstrated to attenuate villus atrophy and increase mucosal DNA content in the rat. This study was performed in order to determine the effects of glutamine supplementation to a balanced TPN mixture (including lipids) on epithelial cell kinetics using autoradiography. Male Sprague-Dawley rats were used. Group 1 (control) received food and an intravenous saline infusion. Group 2 received an intravenous TPN mixture including lipids but without glutamine. The same TPN mixture, glutamine replacing an isonitrogenous amount of non-essential amino acids, was given to Group 3. Animals were fed for 7 days, whereafter blood and intestinal samples were taken 1 h after injection of tritiated thymidine. Microscopy of specimens from proximal jejunum revealed a significant reduction in the number of cells in crypts and villi in both TPN groups (2 and 3) compared to orally fed animals (p < 0.001). Epithelial cell numbers were not significantly different in Group 2 and 3. Similarly, the labelling index (number of labelled cells/number of crypt cells) was not affected by glutamine administration. In plasma, glucagon concentrations in Group 2 (TPN without glutamine) seemed to decrease compared to Group 1 and 3 (p = 0.06). In this study, glutamine supplementation did not affect apithelial atrophy or cell proliferation. It is concluded, that the effects of glutamine on mucosal atrophy and renewal in jejunum may depend on the composition of the TPN mixture supplied during parenteral feeding.