L-Glutamine is the primary metabolic fuel of the intestinal mucosa. This in vivo study compares the effect of L-glutamine 50 mM with that of D-glucose 50 mM on water and electrolyte absorption in jejunal and ileal loops of healthy rabbits. Using polyethylene glycol (PEG) as a nonabsorbable marker and an incubation at 37 degrees C, we found that absorption of water (P = 0.000), sodium (P = 0.002), potassium (P = 0.001), and chloride (P = 0.003) from the glutamine electrolyte solution was greater than from the glucose electrolyte solution in the ileum. A similar trend was shown in the jejunum. We conclude that L-glutamine may be a useful component to be tested in oral rehydration solutions for treating diarrheal dehydration.