REGENERATING PERIPHERAL AXONS TRANSPORT AND RELEASE LOW-MOLECULAR-MASS MATERIALS IN-VITRO

The release of radiolabeled material from regenerating frog sciatic ne rves was studied using a multicompartment chamber, in which the gangli a and the outgrowth region, respectively, were separated from the rest of the nerve. The nerves were incubated with radioactive amino acids in the ganglionic compartment, and the material transported to and rel eased at the outgrowth region was collected and analyzed. Approximatel y 10% of the transported radioactivity was released over a 24-h incuba tion period. Of the released materials, 84% had a molecular mass of <1 ,000 daltons [the low-molecular-mass (LM) fraction] as determined by e xclusion chromatography. The presence of LM material could not be expl ained by leakage, nor was it due to intracellular or extracellular deg radation of radiolabeled, transported proteins. It was reduced by cold and was shown by the use of vinblastine to be dependent on axonal tra nsport. According to TLC, both the original precursor and metabolites thereof could be detected among the released LM material. The present results demonstrate the existence of a transport system for LM materia l in peripheral axons. The preferential release of LM over high-molecu lar-mass material at the outgrowth region suggests that it could serve specific functions during regeneration.