Inhibition of polyamine oxidase in rats improves the sensitivity of urinary polyamines as markers for cell death.

In this study we investigated polyamine metabolism during inhibition of two polyamine-catabolizing enzymes. This was performed by treating rats with aminoguanidine [an inhibitor of Cu-dependent amine oxidase (CuAO)], NN'-bis(buta-2,3-dienyl)butane-1,4-diamine [MDL 72527, an inhibitor of FAD-dependent polyamine oxidase (PAO)], tetrachloromethane (hepatotoxic agent) and combinations of these compounds. Emphasis was laid on the origin and possible clinical usefulness of two polyamine metabolites: acetylisoputreanine-gamma-lactam and N1N12-diacetylspermine. Acetylisoputreanine-gamma-lactam is a normal constituent of human and rat urine. Treatment of rats with aminoguanidine led to undetectable urinary levels of acetylisoputreanine-gamma-lactam, whereas MDL 72527 treatment resulted in a 12-fold increase. Under normal conditions this compound represents a minor CuAO catabolite of N1-acetylspermidine, but may become of more importance under CuAO-induced conditions. N1N12-diacetylspermine was undetectable in urine samples from non-pregnant adults and rats, but became detectable after treating rats with MDL 72527. Additional tetrachloromethane poisoning resulted in a 35-fold increase of N1N12-diacetylspermine in urine and its appearance in liver. Hence urinary excretion of N1N12-diacetylspermine during PAO inhibition may serve as a sensitive marker for cell death. This was confirmed by myeloid-leukaemia-bearing rats treated with MDL 72527, which also excreted N1N12-diacetylspermine in urine in relatively high amounts from at least day 14 until spontaneous death.