Small intestinal growth caused by feeding red kidney bean phytohemagglutinin lectin to rats

Background: Plant lectins are present in significant quantity in a variety of food sources. The aim of this study was to determine if they stimulated growth of the intestine. Methods: Germ-free and conventional rats were pair fed purified phytohemagglutinin lectin (PHA) or equivalent casein in a fully nutritious diet. PHA was instilled into in situ jejunal and ileal loops. Organ weight, length, DNA, protein content, morphometry, and [³H]thymidine uptake into jejunal crypt cells were measured. Results: A trophic response occurred in the small intestine (jejunum greater than ileum) because of PHA (P < 0.001), was sustained by continued exposure, and was reversible on reinstitution of the control diet (P < 0.05). The intestinal microbial flora in conventional animals that were fed PHA augmented the growth-stimulatory effects of PHA on intestinal weight (P < 0.01). PHA caused fecal protein, fat, and mucous glycoprotein levels (P < 0.001) to increase in germfree animals. PHA increased jejunal mucosal crypt depth and crypt mitotic activity (P < 0.05); DNA content (P < 0.05) and [³H]thymidine uptake (P < 0.01) into crypt cells was increased. No increase in plasma or tissue content of gastrin, enteroglucagon, or peptide YY was observed on PHA exposure, and there was no increase in organ weight of the liver, kidney, or colon. Conclusions: PHA stimulated growth of rat small intestine when present in the diet or instilled in the bowel lumen.