Relationship between Survival and Binding of Plant Lectins during Small Intestinal Passage and Their Effectiveness as Growth Factors

Abstract

The effects on the small intestine and the growth of rats of six pure plant lectins: PHA (Phaseolus vulgaris); SBL (Glycine maxima); SNA-I and SNA-II (Sambucus nigra); GNA (Galanthus nivalis) and VFL (Viciafaba), covering most sugar specificities found in nature, were studied in vivo. Variable amounts, 25% (VFL) to 100% (PHA, GNA) of the lectins administered intragastrically, remained in immunochemically intact form in the small intestine after 1 h. All lectins, except GNA, showed binding to the brush border on first exposure, although this was slight with VFL. Thus, binding to the gut wall was not obligatory for resistance to proteolysis. Exposure of rats to lectins, except VFL, for 10 days, retarded their growth but induced hyperplastic growth of their small intestine. The two activities were directly related. PHA and SNA-II, whose intestinal binding and endocytosis was appreciable after 10 days of feeding the rats with diets containing these lectins and similar to that found on acute (1 h) exposure, were powerful growth factors for the small intestine. GNA, which did not bind at the start but was reactive after 10 days, and SNA-I, which behaved in the opposite way, induced changes in receptor expression in the gut. As they were bound to the brush border transiently, they were less effective growth factors. VFL was not bound or endocytosed, was non-toxic and did not promote gut growth.

Inhibitory action of a new lectin from Xerocomus chrysenteron on cell-substrate adhesion

“…Other lectins have already been shown to rapidly cover cell and tissue surfaces. Epithelial cells from several insect guts were found to be covered by Galanthus nivalis (GNA) and Con-A lectins added to the insect diet [17,18]. The accumulation and persistence of lectins on cell and tissue may additionally act by disrupting the multiple metabolic processes carried out by this cell or this tissue [18].…”

Lectins as Plant Defense Proteins

“…Ingested PHA, which is highly resistant to gut proteases, binds to the brush border cells of the intestine where it is rapidly endocytosed. When the lectin enters the cells, it induces an enhanced metabolic activity that eventually leads to hyperplasia and hypertrophy of the small intestine (Pusztai et al, 1990). Moreover, ingestion of PHA or raw beans causes acute nausea followed by vomiting and diarrhea.…”

Soybean: feed quality and safety. Part 2: Pathology of soybean feeding in animals. A review

“…However, small intestinal weight and structure are not influenced by camostate (unlike raw soybean meal), which suggests disparate effects on small intestine and pancreas. Pusztai et al (1990) reported on the intestinal growth promoting effect of lectins in rats and suggested that lectins might play a role in the replacement of epithelial cells. Trypsin inhibitors can only partially account for the antinutritive effects as it was demonstrated by DiPietro and Liener (1989).…”