Effect of α1-adrenergic blockade on canine ileal water, electrolyte, and glucose absorption

Abstract

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.

Epithelial distribution of neural receptors in the guinea pig small intestine

“…Results are expressed as mean ± SE, n = 5-9. guinea pig jejunum. Although it has been suggested that both αand βadrenergic receptors mediate transport (Barry et al 1994a(Barry et al , 1994bDiaz-Sampedro et al 1998;Vieira-Coelho and Soares-da-Silva 1998), the distribution of α 1 -and βadrenergic receptors is poorly characterized. Dopamine increases absorption in both in vivo (Barry et al 1995;Donowitz et al 1983;Sjovall et al 1984;Wahawisan et al 1985) and in vitro models (Donowitz et al 1982), and receptors for dopamine have been localized to the intestinal mucosa (Hernandez et al 1987;Marmon et al 1993), including the villus and crypt epithelium (Vaughan et al 2000).…”