Agmatine modulates the in vivo biosynthesis and interconversion of polyamines and cell proliferation

Agmatine has recently gained wide interest as a bioactive arginine metabolite with a multitude of physiological functions. This study evaluates the in vivo role of agmatine in the modulation of metabolism and intracellular level of polyamines. Here, we report that agmatine, administered to mice, differentially affects the renal and liver activity of the two key enzymes regulating polyamine biosynthesis and interconversion/degradation. Thus, agmatine exerts a negative regulation of ODC activity and protein content, and positive regulation of SSAT activity, having no effect on ODC and SSAT transcript level. Agmatine modulation of ODC and SSAT activities is noticeably augmented by the inhibitor of its catabolism, aminoguanidine. Antizyme and eIF4E protein content appears to be affected by agmatine only insignificantly and apparently do not contribute to agmatine-induced down-regulation of ODC content. The homeostasis of spermidine and spermine is preserved after agmatine injection, while the putrescine level decreases. Furthermore, when tested in a mouse kidney injury model, agmatine, partially but significantly, reduces [3H] thymidine incorporation into DNA. This is consistent with suppressed renal tubule epithelial cell proliferation. The findings provide in vivo evidence of a substantial role of agmatine as a modulator of polyamine biosynthesis and degradation and suggest its suppressive effect on cell proliferation.