Synthesis and uptake of no carrier-added C-11 labeled putrescine in male rat prostate

For the past several years there has been interest in the potential use of aliphatic polyamines in tumor localization and prostate imaging employing C-11 labeled methylated derivatives and carrier-added C-11 labeled putrescine. This study was undertaken to develop a no carrier-added (NCA) synthesis of C-11 labeled putrescine (C-11-putrescine), and to compare the uptake into rat prostate with carrier-added C-11-putrescine and C-14-putrescine. NCA C-11-putrescine was prepared by a two step synthesis involving first the reaction of C-11-cyanide (500 Ci/mmol) with 3-bromopropionitrile followed by reduction of the intermediate, C-11-succinonitrile, with boron-methyl sulfide. Separation of the desired product was performed by HPLC using a quaternary ammonium anion exchange column. Radiochemical yields of 2-10% (corrected) were obtained in an overall synthesis time of <60 minutes. NCA C-11-putrescine uptake in the ventral prostate of mature male rats at one-hour post injection showed significantly higher uptake (1.8 %ID/g) compared with the uptake of C-11-putrescine containing ''cold'' putrescine in concentrations ranging from 2.8 μmol/kg (.18 %ID/g) to 0.3 nmol/kg (.31 %ID/g) injected. Prostate uptake was also higher when compared with the uptake of C-14-putrescine (.08 nmol/kg injected: .16 %ID/g) determined from earlier studies. Significantly higher values of prostate to non-target tissue (muscle) was also obtained with the NCA material. These results indicate that the effect of carrier-added putrescine at concentrations as low as .08 nmol/kg is to saturate the mechanism of uptake into prostate