AXONAL TRANSPORT OF LIPIDS IN THE RABBIT OPTIC SYSTEM

Abstract— Axonal transport of lipids was demonstrated in the rabbit optic system using 2-³H]glycerol and 3-¹⁴C]serine. Following intraocular injection of these precursors, radioactive lipids were detected in the optic tract, superior colliculus and lateral geniculate body over a 31 day period. The bulk of lipid appeared to migrate at a rate equivalent to that of rapidly transported protein which, when combined with a prolonged period of release into the axon, led to a peak of transported radioactivity at 6-10 days for the 3 tissues. The suggestion of a second peak at 17 days indicated the possibility of a smaller slow component, although another interpretation is suggested. Analysis of individual transported lipids revealed 2-³H]glycerol to label phosphoglycerides preferentially and 3-¹⁴C]serine to be an effective precursor for sphingolipids and certain of the phosphoglycerides. 3-¹⁴C]Serine labeled axonally transported proteins to an even greater extent than lipids, revealing the same fast and slow components previously shown with other amino acids.