Insulin-like growth factor-I stimulates Na+-dependent glutamine absorption in piglet enterocytes

Agents that enhance intestinal glutamine transport may be useful under conditions in which intestinal mucosal function is compromised. Here we examined whether oral administration of insulin-like growth factor (IGF-I) stimulates absorption of L-glutamine in piglet intestine. Colostrum-deprived piglets received human recombinant IGF-I (3.5 mg/kg/day) or vehicle orogastrically every 8 hr for four days after birth. Piglets were killed on day 5 and the proximal jejunum was removed. Basal electrical parameters and L-glutamine-stimulated changes in short-circuit current were measured in muscle-stripped tissues, and rates of L-glutamine uptake were measured in everted jejunal sleeves. Oral IGF-I had no effect on jejunal mucosal mass. Short-circuit current responses to mucosal addition of 10 mM L-glutamine were increased by oral IGF-I. Total and carrier-mediated uptakes of L-glutamine per milligram were greater in tissues from IGF-I-treated piglets due to a significantly greater maximal rate of uptake (Jmax). Thus, oral administration of IGF-I stimulates Na+-dependent glutamine absorption in piglet small intestine, an effect that is independent of changes in intestinal mucosal mass.