Alteration of intestinal putrescine uptake in tumour-bearing rats

Polyamines are essential for rapidly dividing cells such as enterocytes and tumour cells. In both cells, polyamine pools are maintained by biosynthetic pathways along with active uptake systems. Because of their strategic position, enterocytes play an important role in the trafficking of luminal polyamines. The aim of this study was to determine whether the high polyamine demanding MAT-LyLu prostatic tumour alter the absorption and metabolism of putrescine in the small intestine tissue of rats. In vivo, after intragastric intubation of [14C]-putrescine, both the uptake of putrescine and its metabolic conversion into non-polyamine metabolites were enhanced in the small intestine of tumour-bearing rats. The presence of the tumour also altered the biodistribution of the radioactivity with a striking increased level of radioactivity in the plasma, which was probably the consequence of a higher net flux of putrescine from the lumen to the blood. Ex vivo studies using everted small intestine segments supported this hypothesis. The stimulation of putrescine uptake and metabolism in enterocytes of tumour-bearing animals may be an adaptation to compensate for the energy deficit caused by the competition with the tumour for nutrients and worsened by the tumour-associated cachexy.