Flow of protein and ribonucleic acid in peripheral nerve.

Radioactively labelled leucine and orotic acid were injected into the ventral horn of the lumbar region of the spinal cord. The outflow of labelled products into the sciatic nerve was studied. Leucine is rapidly incorporated into protein and to a lesser extent into lipid. The labelled protein is transported down the nerve, apparently by axoplasmic flow. This labelled protein was present in all sub-cellular fractions of nerve although the soluble fraction had the highest specific activity. Orotic acid is converted to a number of nucleotide derivatives and RNA. Both the nucleotides and RNA move down the sciatic nerve, but the pattern of movement is diffuse whereas protein appears to move as a discrete band. The results suggest that two systems may be operating, one in which part of the RNA is transported by axoplasmic flow along the nerve and the other involving a synthesis of RNA in the nerve from precursors which flow down the nerve. This labelled RNA was membrane bound and on sedimentation analysis, proved to be predominantly of ribosomal type.