Stimulation of jejunal mucosal protein synthesis by luminal glucose. Effects with luminal and vascular leucine in fed and fasted rats.

This study was conducted to determine whether short-term (1.75 h) luminal glucose perfusion increases the mucosal protein synthesis rate in rat small intestine. A luminal perfusate containing 56 mM glucose was compared with a control perfusate containing mannitol in two jejunal segments constructed in the same animal. Mucosal protein synthesis rates were determined when the tracer amino acid was administered intravenously and intraluminally. The results indicated that luminal glucose perfusion rapidly stimulated mucosal protein synthesis in the fed state by 20% and 37% with the labeled amino acid derived from the vascular and luminal compartment, respectively. A 16-h fast abolished the stimulatory effect of glucose when the labeled amino acid was given intravascularly but not intraluminally. These effects of glucose could be ascribed to a direct alteration of mucosal metabolism rather than to indirect systemic effects.