Postprandial absorptive augmentation of water and electrolytes in the colon requires intraluminal glucose

Abstract

Postprandial absorptive augmentation of water and electrolytes occurs in the small intestine and colon. The role of intraluminal nutrients in this response is poorly understood. Our aim was to determine whether postprandial absorptive augmentation of water and electrolytes in the colon requires the presence of intraluminal glucose. Four adult dogs underwent enteric isolation of a 50 cm segment of proximal colon. An ileal-like electrolyte solution (Na⁺, 130 mEq/L; K⁺, 10 mEq/L; Cl^-, 115 mEq/L; and HCO₃ ^-, 25 mEq/L), alone or containing glucose (10 mmol/L), was infused at 4 ml/min into the colonic segment. Experiments were performed during fasting and postprandially after a 400 Kcal mixed-nutrient meal. Effluent was collected in 60-minute intervals after steady state was achieved. Net absorptive flux of water was increased in the presence of intraluminal glucose during the fasted state (11 ± 0.8 vs 7.4 ± 0.9 µl/min/ cm, P < 0.01). The net absorptive flux of water and electrolytes increased postprandially only in the presence of intraluminal glucose (P < 0.05). Our finding that glucose augments both baseline and postprandial absorption of water and electrolytes in the proximal colon suggests that luminal factors have a role in postprandial absorptive augmentation. Whether this is specific to glucose or occurs with other nutrients remains to be determined.