EFFECT OF ALPHA(1)-ADRENERGIC BLOCKADE ON CANINE ILEAL WATER, ELECTROLYTE, AND GLUCOSE-ABSORPTION

Meal ingestion stimulates an increase in small intestinal water and el ectrolyte absorption. Endogenous norepinephrine may at least partially mediate this meal-stimulated proabsorptive response. Luminally admini stered alpha(1)-adrenergic agonists such as norepinephrine and phenyle phrine cause significant small bowel absorption, which can be prevente d by the selective alpha(1)-adrenergic antagonist terazosin. This stud y tested two hypotheses: (1) a meal stimulates ileal water, electrolyt e, and glucose absorption; and (2) meal-stimulated ileal absorption is mediated via alpha(1)-adrenergic receptor activation. Absorption stud ies (N = 27) were performed on dogs with 25-cm ileal Thiry-Vella fistu las (TVF). Perfusion with [C-14]PEG was used to calculate absorption o f water, electrolytes, and glucose from the TVF. Three groups were ran domly 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 me al 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 sign ificantly alter basal or meal-stimulated ileal absorption. In conclusi on, meal ingestion stimulates ileal absorption of water, electrolytes, and glucose. Neither basal nor meal-stimulated ileal absorption is al tered by alpha(1)-adrenergic receptor blockade. These data suggest tha t nonadrenergic neural pathways or humoral factors are the likely medi ators of meal-induced intestinal absorption.