A STUDY ON THE METABOLISM OF SPERMIDINE IN MAMMALS - PURIFICATION ANDIDENTIFICATION OF A NEWLY IDENTIFIED METABOLITE, 2-OXO-1-PYRROLIDINEPROPIONIC ACID, IN RAT URINE

In order to study the metabolism of spermidine in mammals, radioactive spermidine was injected intraperitoneally into a rat and urine was co llected for analysis. Incorporation of radioactivity into putreanine, isoputreanine, spermidic acid, and N-aminopropylpyrrolidin-2-one was c onfirmed by ion-exchange chromatography, thin layer chromatography, an d paper electrophoresis, the highest radioactivity being observed in t he non-polar and acidic fraction of the collected urine. A radioactive compound was purified from the non-polar and acidic fraction, and ide ntified as 2-oxo-1-pyrrolidinepropionic acid by comparison of its beha vior on ion-exchange chromatography and thin layer chromatography with that of authentic 2-oxo-1-pyrrolidinepropionic acid, and recrystalliz ation with the authentic compound. Acid hydrolysis of the radioactive compound produced radioactive spermidic acid, confirming the identific ation. To examine the interconversion between isoputreanine and N-amin opropylpyrrolidin-2-one, these compounds were deuterated and then intr aperitoneally injected into a rat. Analysis of 24-h urine by gas-chrom atography-mass-spectrometry indicated no interconversion between the t wo metabolites of spermidine under these conditions. An intracerebrove ntricular injection of radioactive spermidine into a rat showed that r adioactivity was also incorporated into the metabolites of spermidine in the brain, and oxidative deamination of the aminopropyl moiety of s permidine was thought to be dominant in the central nervous system and vice versa in peripheral organs.