Duodenal toxicity of dietary Phaseolus vulgaris lectins in the rat: an integrative assay.

It is now generally admitted that phytohemagglutinin (PHA) constitutes the main factor responsible for the dietary toxicity of raw kidney beans. In the growing rat, an impairment of growth is the unique expression of a malnutrition syndrome. The aim of this work was to precise to what extent the intestinal injuries may account for this malnutrition. PHA was administered for 9 days to growing rats at levels ranging from 0.0025 to 0.25% of food dry matter. One group of controls was fed ad libitum and other groups were restrained. In such conditions, PHA reduced the food intake when offered at a level higher than 0.04% as a linear function of the logarithm of lectin rate. Intestinal injuries were also dose-dependent: blebbing of microvilli and loss of alkaline phosphatase occurred at the smallest dose of PHA, cell loss occurred at higher doses. A compensatory hyperplasia was observed as a consequence of both intestinal injury and reduced food intake. Our main results are that, whatever may be the damages caused to the duodenal mucosa, the observed growth impairment was quasi-totally imputable to the reduction of food intake.