Axonal Transport of Lipids in the Rabbit Optic System

Axonal transport of lipids was demonstrated in the rabbit optic system using [2‐ 3 H]glycerol and [3‐ 14 C]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‐ 3 H]glycerol to label phosphoglycerides preferentially and [3‐ 14 C]serine to be an effective precursor for sphingolipids and certain of the phosphoglycerides. [3‐ 14 C]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.