Role of Na⁺-glucose cotransport in jejunal meal-induced absorption

In awake dogs, meal ingestion stimulates the absorption of water and electrolytes from neurovascularly intact jejunal Thiry-Vella loops, even though these loops are isolated from the remainder of the gut. This study was designed to investigate the role of Na⁺-glucose cotransport in mediating this event. Meal ingestion enhanced absorption when the jejunal lumen was perfused with an isotonic solution containing D-glucose, D-galactose, or 3-O- methylglucose. This response was absent when the perfusate contained mannitol or when phlorizin was added to the D-glucose solution. Mucosa from the jejunal loops was serially biopsied and assayed for brush-border Na⁺-glucose cotransporter (SGLT1) mRNA and protein expression. Although no changes in SGLT1 mRNA levels were observed, protein levels significantly increased within 30 min following meal ingestion. The time course of SGLT1 protein expression corresponded with that of increased Na⁺ and water absorption. These results suggest that meal-stimulated jejunal absorption may be mediated through an induction of mucosal SGLT1.