Effects of soy protein diet on digestive lumenal polyamines and colonic cell proliferation in pigs.

This study was performed to determine whether erythrocyte and digestive lumenal polyamine concentrations are affected by a soy protein diet when compared to a casein diet. We also determined the effects of these diets on colonic cell proliferation. Sixteen pigs received either a 16% soy protein or casein diet for 25 days. The erythrocyte putrescine was higher in pigs fed the soy protein diet. Significant levels of polyamines were observed in the digestive lumen on both diets. Lumenal putrescine and cadaverine were higher in the proximal colon in the casein group. Lumenal spermidine was higher in the caecum and colon in the soy protein group. No significant differences in the ornithine decarboxylase activity nor in the proliferative cell nuclear antigen labelling index were observed in the colonic mucosa regardless of the regimen. These results indicate that the dietary source of protein induces significant changes in lumenal polyamines in the colon. The physiological effects of these changes need to be further investigated.

Effects of a high soy protein diet on intestinal polyamines and ornithine decarboxylase activity in rats.

This study was performed to determine whether intestinal luminal polyamine concentrations are affected by a high soy protein diet when compared with a high casein diet or a normoprotein casein diet. We also determined the effects of these diets, with differences in polyamines content, on mucosal polyamines and ornithine decarboxylase (ODC) activity to assess cell proliferation. Three groups of eight male Wistar rats were fed either a 50% soy protein diet, a 50% casein diet, or an 18% casein diet as a control. After 4 weeks of feeding, both intestinal content and mucosa were recovered. Polyamines were assayed by high performance liquid chromatography. ODC activity was measured by the release of (14)CO(2) from (14)C-L-ornithine. Luminal putrescine and cadaverine concentrations were higher in the jejunum than in the ileum, suggesting an absorptive process. The highest concentrations of intestinal polyamines were observed in rats fed the soy protein diet (P < 0.05). Only minor differences were observed in mucosal polyamines according to the diets. ODC activity was also higher in the intestinal mucosa of rats fed the high soy protein diet (P < 0.05). These results suggest that intestinal luminal polyamine concentrations and ODC activity are modulated by the dietary protein source.