Fractionation of protein carried by axoplasmic transport. II. Comparison in the rat of proteins carried to the optic relay nuclei.

Proteins carried in the fast (200 mm/day) axoplasmic flow of retinal ganglion cells in albino rats were labeled with intraocular injections of radioactive L-methionine. Transported proteins which accumulated in the lateral geniculate nuclei (LGN) and superior colliculi (SC) 4 1/2 hours after injection were extracted with media of increasing solubilizing power. Over 70 percent of the transported material is soluble only in media possessing detergents such as Triton X-100 and sodium dodecyl sulfate. Specific activities of the transported proteins exceeded 7000 dpm/mg. With specific activities this high, further fractionation could be carried out under conditions of high resolution. Separations of solubilized proteins on polyacrylamide gels, either with or without detergents, showed that a large number (60-100) of polypeptides are transported. Using a double labeling procedure which employed L-[35S]methionine and L-[methyl-3H]methionine, material transported to the LGN was compared with that transported to the SC. No statistically significant differences were seen in the polypeptides transported by the retinal ganglion cells to the two major optic relay nuclei.