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.