Procyanidin from Black Beans (Phaseolus vulgaris) Inhibits Nutrient and Electrolyte Absorption in Isolated Rat Ileum and Induces Secretion of Chloride Ion

Abstract

Dietary tannins are reported to impair the absorption of nutrients and minerals in whole animals and in semi-isolated intestinal preparations. The present studies investigated the effect of purified procyanidin from black beans (Phaseolus vulgarus) on tissue electrical parameters, isotopic Na⁺ and Cl^- fluxes and Na⁺-dependent absorption of labeled glucose by isolated rat ileum. In short-circuited ileal preparations, 0.5–2 g/L procyanidin (PC) inhibited Na⁺ and Cl^- absorption and stimulated Cl^- secretion, with consequent increases in short circuit current (I_sc), total tissue conductance and transepithelial voltage. The effect was not blocked by indomethacin (20 µmol/L). Also, PC significantly inhibited the glucose-dependent and phlorizin-sensitive component of I_sc; a similar result was obtained for the alanine-dependent fraction of I_sc. In everted ileal sacs PC inhibited Na⁺-dependent uptake of labeled glucose, but not passive uptake, by a noncompetitive mechanism. The effects of PC are reminiscent of those of recognized intestinal secretagogues and suggest that the antinutrient effects of condensed tannins involve stimulation of intestinal secretion at the expense of absorption. The results argue against use of black bean broth or cooking liquor in rehydration media for treatment of secretory diarrhea.