ISOCALORIC GLUTAMINE-FREE DIET AND THE MORPHOLOGY AND FUNCTION OF RATSMALL-INTESTINE

Background: The importance of L-glutamine as metabolic fuel for entero cytes and its role in prevention of mucosal atrophy during total paren teral nutrition is well documented. No data are available to date that document whether a glutamine-free complete enteral diet, requiring fu ll energy expenditure for hydrolysis and absorption, is associated wit h changes in the morphology and function of the small intestine. Our a im was to examine the effect of such a diet during a 4-week period on the morphology and function of the small intestine of rats. Methods: T hree isocaloric solid rat food, containing 0%, 4%, and 8% of glutamate , respectively, were fed to three groups of rats. On the 7th and 28th days the morphology of the jejunum, the subcellular structure of enter ocytes on transmission electron microscopy, enzyme activities, blood, and muscle glutamine were examined and compared in the three groups. R esults: The rats on the glutamine-free diet had significantly lower mu cosal wet weight, protein and DNA content, and number of intraepitheli al lymphocytes on the 7th day, whereas the number of mitoses in the Li eberkuhn's crypts was significantly less on the 28th day. The height o f the enterocytes and villi was 20% higher on average in the glutamine -free group. Electron microscopy revealed either early (swelling of cr istae) or terminal (swelling of matrix) mitochondrial degenerative cha nges, homogenization of apical cytoplasm, and degeneration and fragmen tation of microvilli with loss of their rootlets. The Na+,K+-ATPase ac tivity was markedly decreased in the glutamine-free group compared wit h that of the other groups, most likely because of a diminished energy supply. Among brush border membrane enzymes, lactase activity decreas ed markedly (p <.05) in the first week. The glutamine-free diet result ed in an increase of the lung glutamine synthetase activity and decrea se in muscle glutamine content by the 28th day of the diet. Conclusion s: Our study shows for the first time that a complete enteral diet, de ficient only in glutamine, is associated with significant early morpho logic and functional changes in the small intestine. The precise effec t on intracellular events and the time of onset of these changes needs to be clarified in the future.