The polyamines, mainly putrescine (PU), spermidine (SPD), and spermine (SPM) (Fig. 1 ), are low molecular mass aliphatic amines that exist in all living organs, and play important roles in cell growth and differentiation ( 1 ). The intracellular concentrations in many cell types are in the submillimolar range, and the maximum increase is less than twofold over the course of a cell cycle ( 2 ). It is well known that ornithine-derived polyamines are implicated in a variety of cell functions involving DNA replication, gene expression, and protein synthesis ( 3 , 4 ). Recent studies demonstrated that ornithine-derived polyamines play roles in potassium depolarized stimulation of synaptic function ( 5 ), determination of tumor malignancy ( 6 ), intercellular messengers ( 7 ), stabilization of membrane structures ( 4 ), and regulated exocytosis ( 8 , 9 ). Fig. 1. The three common polyamines.
