The Toxicity of High-Gliadin Diets. Studies on the Dog and on the Rat

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Abstract
In the present study it was possible to produce convulsive reactions in all of six dogs fed high-gliadin diets in which gliadin was the sole protein and furnished 16% or more of the caloric intake. Intestinal parasites were ruled out as possible cause of the toxic reactions. The fact that there was an initial lag in the appearance of gliadin toxicity and a delay in the disappearance of the seizures suggests the accumulation of some toxic substance during the gliadin feedings and its subsequent elimination. The increases in blood non-protein nitrogen were not sufficiently large to indicate that the convulsions were uremic in nature. Various experiments tentatively suggest that this toxicity of the high-gliadin diets may be due to a protein sensitization. The gliadin, isolated from a 75% alcoholic extract of gluten flour, contained only 0.15% ash. Selenium was not present as a contaminant of the protein. Insofar as growth data are concerned, feeding experiments showed that the gliadin was free of any substance toxic for the growing rat. No convulsive reactions were observed in the rats subsisting on a gliadin diet in which the protein furnished as much as 25.6% of the caloric intake. Apparently susceptibility to gliadin toxicity is a species characteristic. The rats, fed the 36% (by weight) gliadin diet, subsisted on a ration containing actually 13.2% glutamic acid. The ingestion of a dietary mixture, containing such a high concentration of this amino acid, appeared to be non-toxic for this species. The nutritional significance of the lysine present in gliadin was emphasized. Rats fed an 18% or a 36% gliadin diet were stunted practically to the same extent. However, when both rations were supplemented with the same amount of lysine, growth was twice as rapid in those animals fed the 36% diet.