UC Irvine

The metabolic fate of putrescine labelled in vivo was investigated after administration of a trace (10−7 M) of L-[14C]ornithine to exponentially growing mycelia of Neurospora crassa, followed by a large chase (2 mM) of L-[12C]ornithine. The specific radioactivities of putrescine and spermidine were determined during the chase period by reaction with [3H]dansyl chloride of known specific radioactivity and isolation of the dansyl-derivatives by thin-layer chromatography. Radioactivity remained in the putrescine pool for over 2 h during the chase period. This suggests that putrescine is largely sequestered (80% or more) in vivo. The metabolic sequestration of polyamines may be a significant factor in the regulation of polyamine synthesis.