Fate of orally administered 15N-labeled polyamines in rats bearing solid tumors

Abstract

We studied absorption, distribution, metabolism, and excretion of polyamines (putrescine, spermidine, and spermine) in the gastrointestinal tract using 15N-labeled polyamines as tracers and ionspray ionization mass spectrometry (IS-MS). The relatively simple protocol using rats bearing solid tumors provided useful information. Three 15N-labeled polyamines that were simultaneously administered were absorbed equally from gastrointestinal tract, and distributed within tissues at various concentrations. The uptake of 15N-spermidine seemed preferential to that of 15N-spermine since the concentrations of 15N-spermidine in the liver and tumors were higher, whereas those of 15N-spermine were higher in the kidney, probably due to the excretion of excess extracellular spermine. Most of the absorbed 15N-putrescine seemed to be lost, suggesting blood and tissue diamine oxidase degradation. Concentrations of 15N-spermidine and 15N-spermine in the tumor were low. We also describe the findings from two rats that were administered with 15N-spermine. The tissue concentrations of 15N-spermine were unusually high, and significant levels of 15N-spermidine were derived from 15N-spermine in these animals.