Axonal transport of phospholipids in rabbit optic pathway

Abstract

The uptake of different labeled precursors, their incorporation into lipids, and transport along the rabbit optic pathway [ipsilateral retina and optic nerve (ON), and contralateral optic tract (OT), lateral geniculate body (LGB), and superior colliculus (SC)] were investigated. Albino rabbits were used. The following radioactive precursors, either combined or separately, dissolved in 50 μl of saline containing 15% BSA, were injected into vitreous body: [2-³H]glycerol (50 μCi), [1-¹⁴C]palmitate (15 μCi), and [1-¹⁴C]linoleate (7.5 μCi). Animals were killed at different time intervals from 1 hr up to 24 days. The radioactivity of total lipids and of different phospholipid classes from total tissue was measured. One hour after the administration of precursors, the radioactivity into the retina was high and the incorporation of [³H]glycerol and [¹⁴C]palmitate increased until 12 hr and 24 hr, respectively. The incorporation of [¹⁴C]linoleate reached a maximum on the second day. The phospholipids of LGB and SC were intensively labeled after 4–8 hr, and their radioactivity increased up to the 10th day after injection, independent of the precursor employed. The results obtained indicate that the labeled hydrophilic and hydrophobic precursors used were actively incorporated into the retina. The phospholipids were later transported at a rapid rate along the optic pathway.