Abstracts
2001 Digestive Disease Week

# 1765 Postprandial Augmentation of Water and Electrolyte Absorption in the Colon Requires Intraluminal Glucose
Michael L. Kendrick, Nicholas J. Zyromski, Karen D. Libsch, Toshiyuki Tanaka, Michael G. Sarr, Rochester, MN

INTRODUCTION: Postprandial augmentation of water and electrolyte absorption occurs in small intestine and colon. The role of intraluminal nutrients in this response is poorly understood.

AIM: To determine if intraluminal glucose is necessary for postprandial augmentation of water and electrolyte absorption. METHODS: 4 adult dogs underwent enteric isolation of a 50-cm proximal colon segment, constructed as a Thiry-Vella loop. An ileal-like electrolyte solution (Na⁺ 125 mEq/L, K⁺ 9 mEq/L, Cl^- 95 mEq/L, HC0₃^- 25 mEq/L) alone or containing glucose (10 mM/L) was infused at 4 ml/min into the enterically isolated colonic segment during the fasted state and postprandially after a 400 Kcal mixed-nutrient meal. Effluent was collected in 30-min intervals for 4 hr after achieving steady state (determined by ¹⁴C marker recovery). Absorptive studies were performed on 4 separate days with each solution. Net absorptive fluxes of H₂0, Na⁺, K⁺ and Cl^- were determined. Data are x±SEM. Paired t-test and ANOVA were applied for comparisons.

RESULTS: Net absorptive flux of H₂0 in colon increased markedly in the presence of intraluminal glucose during the fasted state (table). Net absorptive fluxes of water and electrolytes increased 1 hr postprandially in the presence but not in the absence of intraluminal glucose (table). Na⁺ and Cl^- followed trends in H₂0 absorption (p=0.05, data not shown).

CONCLUSIONS: Intraluminal glucose augments baseline absorption of water and electrolytes in the proximal canine colon. Postprandial absorptive augmentation of water and electrolytes occurs despite enteric isolation, but requires the presence of intraluminal glucose. This suggests that luminal factors in addition to neurohumoral factors control the postprandial absorptive augmentation in the proximal canine colon.

Postprandial

Fasting 1 hr 2 hr 3 hr 4 hr

Basal 7.5±0.9 8.3±1 8.4±0.7 8.5±0.5 7.6±0.9

Basal + glucose 11±0.9* 12.1±0.9** 13..3±1.1** 13.8±0.9** 14.6±0.8**

Absorptive flux of H₂O (mL/min/cm)±SEM, n=4 dogs.

*p<0.01 vs basal solution fasting. **p<0.01 vs basal + glucose fasting.