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The concentration of polyamines contained in the lumen of the gut was quantified. The duodenum and jejunum of the rat contained 2-3 mM putrescine and 1-2 mM cadaverine, whereas in the ileum and colon the concentration of these polyamines was significantly less. In addition, the concentrations of spermine and spermidine in the intestinal lumen were low to undetectable. Putrescine in the lumen of the gut was over 90% free with only 10% or less bound to protein. The activity of the enzymes responsible for the synthesis of polyamines was also measured. In contrast to concentration, enzyme activity was found to be high in the ileum, cecum, and colon and nonexistent in the duodenal and jejunal lumen. This suggested the potential for enterohepatic circulation of polyamines that were synthesized by the colonic microflora and transported to the proximal gut via the portal circulation and biliary tree. Indeed, when [14C]putrescine was instilled into the lumen of the gut, it was secreted in pancreaticobiliary secretions. Upper and lower jejunum and colon all supported enterohepatic circulation of polyamines, whereas it was absent in the ileum. Polyamine accumulation in IEC-6 cells grown under in vitro conditions was also measured. Putrescine was transported under time- and temperature-dependent but sodium-independent conditions. The transporter displayed little selectivity for the various polyamines and compounds with related structures but did not recognize amino acids. The Michaelis constant for putrescine accumulation was 1.26 x 10(-6) M with a maximal velocity of the enzyme reaction of 5,184 pmol putrescine.mg protein-1.h-1.(ABSTRACT TRUNCATED AT 250 WORDS)

Experiments were designed to determine the role of microflora-derived intraluminal polyamines in the colonic mucosal response to obstruction. Sprague-Dawley rats were treated per os with 0.9% NaCl or a combination of nonabsorbable antibiotics prior to the placement of either a sham or complete colonic obstruction. Sixty-six hours after surgery, wet tissue weight, DNA, RNA, and protein content were all increased in the mucosa proximal to the obstruction in NaCl-treated animals; however, DNA content was the only parameter increased after antibiotics. This induction was a purely local effect as neither hyperplasia nor hypertrophy was observed in the ileum or colon distal to the obstruction. In the NaCl-treated animals, mucosal ornithine decarboxylase activity was not induced until 48 h postsurgery, yet mucosal spermidine concentrations were significantly higher as early as 24 h. Intraluminal bacterial lysine, ornithine, and arginine decarboxylase activities were induced by obstruction but were reduced by antibiotic treatment. [14C]putrescine uptake by intestinal epithelial cells (IEC-6) in culture was blocked by the antibiotics employed in this study, but [14C]-lysine transport was relatively unaffected. These data demonstrate that intraluminal polyamines modulate the trophic response of the colonic mucosa after colonic obstruction.

Either ethylamine or the diamine putrescine was infused at the rate of 1 mumol/h for 66 h into the ileal lumen of rats. Total mucosal RNA, DNA, and protein content was greater in amine-treated rats than in rats receiving 0.9% NaCl. Growth was greatest in the mucosa surrounding the tip of the infusion catheter but was also observed 9 cm proximal and distal to the catheter tip. Infusion of these amines induced the activity of the enzymes ornithine and S-adenosylmethionine decarboxylase. Ornithine decarboxylase activity was increased 2- and 6-fold and S-adenosylmethionine decarboxylase activity 10- and 5-fold by putrescine and ethylamine, respectively. Induction of the polyamine biosynthetic enzymes was not accompanied by increases in the tissue content of polyamines. Putrescine, spermidine, and spermine content of the ileal mucosa surrounding the catheter tip was the same in 0.9% NaCl-, ethylamine-, and putrescine-treated animals. Finally, ethylamine was without effect on serum gastrin concentration in these experiments. The results suggest that amines regulate mucosal growth and may do so by modulating the activity of the enzymes involved in the synthesis of the polyamines.

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