Effect of alpha 1-adrenergic blockade on canine ileal water, electrolyte, and glucose absorption

Meal ingestion stimulates an increase in small intestinal water and electrolyte absorption. Endogenous norepinephrine may at least partially mediate this meal-stimulated proabsorptive response. Luminally administered alpha 1-adrenergic agonists such as norepinephrine and phenylephrine cause significant small bowel absorption, which can be prevented by the selective alpha 1-adrenergic antagonist terazosin. This study tested two hypotheses: (1) a meal stimulates ileal water, electrolyte, and glucose absorption; and (2) meal-stimulated ileal absorption is mediated via alpha 1-adrenergic receptor activation. Absorption studies (N = 27) were performed on dogs with 25-cm ileal Thirty-Vella fistulas (TVF). Perfusion with [14C]PEG was used to calculate absorption of water, electrolytes, and glucose from the TVF. Three groups were randomly studied over 4 hr: (1) terazosin alone, (2) meal alone, and (3) terazosin plus meal. Terazosin (10(-4) M) was administered to the TVF in groups 1 and 3 following the first hour. A 480-kcal mixed canine meal was ingested at the end of the second hour in groups 2 and 3. Ileal water, electrolyte, and glucose absorption increased significantly in response to meal ingestion (P < 0.05). Luminal terazosin did not significantly alter basal or meal-stimulated ileal absorption. In conclusion, meal ingestion stimulates ileal absorption of water, electrolytes, and glucose. Neither basal nor meal-stimulated ileal absorption is altered by alpha 1-adrenergic receptor blockade. These data suggest that nonadrenergic neural pathways or humoral factors are the likely mediators of meal-induced intestinal absorption.