Oral toxicity of Kintoki bean (Phaseolus vulgaris) lectin.

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Abstract
There are several antinutritive factors in the Kintoki bean such as lectin, trypsin inhibitor, lack of Met, etc. Lectin was mainly responsible for the growth impairment of experimental animals orally fed raw Kintoki bean. Mice fed raw Kintoki bean as the only protein source lost their body weight and died in 8 days, while mice fed the heated bean grew normally. When mice on a 10% albumin diet ingested 20, 40 or 60 mg Kintoki bean lectin by daily stomach-feeding, their body weights were reduced to 84, 74 or 71% of the control group after 5 days, respectively, and some did not live to complete the experiment. The apparent rates of the intestinal absorption of carbohydrate, lipid and protein were considerably reduced when rats were fed a diet containing 0.4% lectin. The rate of protein absorption was decreased to 26.3% from 55.5% of the control rate. The main tissues of mice that had ingested Kintoki bean lectin by stomach-feeding were subjected to microscopic observation. No changes were observed in the liver, kidney, spleen and pancreas. In the small intestine, the epithelial cells lining the villi were considerably disordered and conspicuously disrupted. The Kintoki bean lectin is one of the most promoting factors for growth impairment in experimental animals and the 1st target organ in the case of oral feeding was the small intestine.