Effects of Soy Protein and Casein Diets on Fecal Enzyme Activity and Histochemistry of Mucin of the Colon

抄録

Protein affects many metabolic processes that are related to tissue growth. Effects of soy protein and casein diets on fecal enzyme activity and histochemistry of mucin of the colon were studied in the present experiments. Male mice were fed a soy protein or casein diet for one month (measurements by histochemistry) or for three weeks (measurements of fecal enzyme activity). Fecal β-glucosidase and β-glucuronidase activities were significantly higher in the mice fed the soy protein diet than in those fed the casein diet. There were significant differences in the histochemical morphology of the crypt of the colon stained with periodic acid Schiff (PAS), alcian blue (AB) at pH2.5, or high iron diamine/alcian blue (HID/AB) at pH2.5 between the mice fed the casein and those given the soy protein one. Granules strongly stained with PAS and AB were more numerous in the area from the middle to the upper part of the crypts in the mice fed the casein diet. However, in the mice fed the soy protein diet, the granules strongly stained with PAS and AB were widely distributed in the area from the lower to the upper part of the crypts. The difference in the histochemical morphology of the colonic crypts observed in our experiment might have been caused by a difference in the metabolism of microflora, by a difference in polyamine catabolism by the microflora, or by a different rate of colonic proliferation between the mice fed the soy protein and those fed the casein. These factors might be compounded to account for the difference in the histochemical morphology of the colonic crypt between the two dietary groups.