Rapid absorption of luminal polyamines in a rat small intestine ex vivo model

Background and Aim: Not only biosynthesis, but also uptake from the intestinal lumen, are important polyamine sources. However, there has been no information regarding dynamic polyamine transport in the small intestine. We evaluated polyamine uptake from the small intestine using a rat ex vivo model. Methods: The organ block consisting of the small intestine and blood vessels was used. The isolated small intestine was placed in a warmed saline bath and perfused in a non-circulating manner via the superior mesenteric artery. Radio-labeled putrescine, spermidine or spermine (7.4 x 10(4) Bq), with 1.0 mL of phosphate buffer saline (pH 7.4) was instilled into the jejunal lumen for 1 min. Blood samples from the portal vein were collected and sample radioactivity was determined. In another experiment, an immunohistochemical study of polyamine was performed. Results: After (14) C-polyamine instillation, radioactivity in the portal vein samples immediately increased and then decreased gradually. The absorptive pattern did not differ among the three polyamines. The recovery rates from radioactivity at the portal vein among the three polyamines were approximately 61-76% during the initial 10 min after the administration of (14) C-polyamine, and were not different from each other. Aminoguanidine, which inhibits putrescine degradation, significantly suppressed initial putrescine uptake and recovery percentage. The intraluminal administration of spermine caused an increase in the immunoreactivity of the spermine antibody in the intestinal villi. Conclusion: Luminal polyamines were rapidly absorbed by the intestinal mucosa and then subsequently transferred into the portal vein using a rat ex vivo model. The prior administration of aminoguanidine significantly inhibited initial putrescine transport into the portal vein. (C) 2003 Blackwell Publishing Asia Pty Ltd.