Axonal Transport of Polyamines in Intact and Regenerating Axons of the Rat Sciatic Nerve

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Abstract
The axonal transport of putrescine or its polyamine derivatives spermidine or spermine is a subject of some debate. [3H]putrescine was injected into the lumbar spinal cord of the rat and the accumulation of radioactivity central to ligatures placed on intact and regenerating sciatic nerves was measured. In normal nerves, approximately twice as much radioactivity built up proximal to these ligatures 2 or 3 days after injection than at more distal ligatures used to control for accumulation of radioactivity which might be due to tissue damage alone. In regenerating nerves the amount of radioactivity accumulating at the ligature was .apprx. 5 times that at the distal ligature and 2-3 times greater than in intact nerves. The identity of the radioactivity in regenerating nerves, determined on an amino acid analyzer, was primarily spermidine and an unknown compound that migrated as a frontal elution peak. Autoradiographic analysis showed that the radioactivity was largely confined to axons, but a significant amount of the silver grains was associated with Schwann cells and myelin sheaths surrounding labeled axons in both intact and regenerating nerves. Evidently, polyamine derivatives of putrescine are transported axonally in rat sciatic nerves and some of this transported material accumulates in Schwann cells surrounding the labeled axons. These processes are apparently augmented during regeneration of the injured axons.