The effect of alimentary polyamine depletion on germ-free and conventional rats

Abstract

Polyamine-deficient semisynthetic diet or polyamine-rich standard rat chow (Altromin 1320) were fed to germ-free and conventional rats to study the influence of alimentary polyamine intake on the endogenous polyamine content and the polyamine formation by the intestinal microflora. Putrescine was the major polyamine in the intestinal contents or feces of germ-free rats. In contrast, the intestinal contents and feces of conventional rats contained mainly spermidine, but only low concentrations of putrescine and spermine. Cadaverine was not detected at all. These polyamine patterns were not affected by the dietary polyamine intake. The polyamine patterns of blood plasma and colonic tissue were similar in germ-free and conventional rats: putrescine was the major polyamine in plasma, whereas spermidine and spermine predominated in colonic tissue. The concentrations of putrescine in plasma and of spermidine and spermine in colonic tissue were lower in rats fed the polyamine-deficient semisynthetic diet than in rats fed the Altromin diet. This difference was greater in germ-free than in conventional rats. Bacteroides, Eubacterium, and Lactobacillus were the predominant organisms of the fecal flora found in conventional rats. The composition of the microflora differed only slightly in response to the diet. In conclusion, (1) putrescine is the main endogenously generated polyamine secreted into the gut lumen, (2) the high spermidine content in the luminal content of all intestinal segments of the conventional rats was independent of the diet and therefore must be of microbial origin, and (3) the intraluminal microbial polyamine formation seems to be inversely related to the alimentary polyamine supply.