Although glutamine is required to maintain gut mucosal metabolism and function, intestinal glutamine uptake from the gut lumen and from the bloodstream is decreased during sepsis. We hypothesized that endogenous mucosal glutamine biosynthesis is increased during endotoxemia, and we attempted to define the "stress" mediators that regulate the activity of small intestinal glutamine synthetase (GS), the principal enzyme of de novo glutamine biosynthesis in the gut.