N-(3-aminopropyl)pyrrolidin-2-one: a physiological excretory product deriving from spermidine

Normal human and rat urine contain N-(3-aminopropyl)pyrrolidin-2-one. This compound was identified by its chromatographic behaviour on a reversed phase column, by thin-layer chromatography of its dansyl derivative, and by mass spectrometry. Evidence for the presence of conjugates of N-(3-aminopropyl)pyrrolidin-2-one in urine was obtained by the fact that partial acid hydrolysis increases the amount of this compound, whereas prolonged hydrolysis leads to its transformation into isoputreanine (N1-(3-carboxypropyl)-1,3-diamino-propane). Although it is likely that the monoacetylderivative of N-(3-aminopropyl)pyrrolidin-2-one is prominent among the conjugates, since this compound can be formed from N1-acetylspermidine, other types of conjugates are also likely. A method is reported suitable for the measurement of N-(3-aminopropyl)pyrrolidin-2-one and of isoputreanine in urine and urine hydrolysates, respectively. Administration of spermidine enhances the amount of urinary excretion of N-(3-aminopropyl)pyrrolidin-2-one. Of 0.1 mmol . kg-1 of spermidine administered intraperitoneally to rats around 12% are transformed into this compound and its conjugates. Treatment of rats with aminoguanidine sulfate, an inhibitor of diamine oxidase, causes a decrease in the excretion of N-(3-aminopropyl)pyrrolidin-2-one and its derivatives. These findings are in agreement with the assumption that N-(3-aminopropyl)pyrrolidin-2-one, the gamma-lactam of isoputreanine, is a physiological degradation product of spermidine. Its formation is catalyzed by an aminoguanidine sensitive, diamine oxidase-like enzyme.