Abstract
AbstractAt different time intervals (4 hr up to 24 days) after intravitreal injection of myo‐(2‐3H)‐inositol, the specific activity (sp act) of phosphatidylinositol (PtdIns) and water‐soluble compounds extracted from the retina, optic nerve (ON), optic tract (OT), lateral geniculate body (LGB), and superior colliculus (SC) was measured. Furthermore, 2 days after biocular injection of the labeled precursor, the specific activity of PtdIns and other major phospholipids in the various subcellular fractions (myelin, axolemma, synaptosomes, mitochondria, and microsomes) purified from ON + OT, from LGB, and from SC was evaluated. In the ON and OT, the phospholipids were labeled 8 hr after the precursor injection; in the LGB and SC after 8–12 hr. In all the optic components examined, the lipid specific activity reached a maximum at day 6 and decreased slowly until day 24 after injection. In the ON + OT, the specific activity of PtdIns, isolated from various subcellular fractions, decreased as follows: myelin > axolemma; in the LGB and SC as follows: microsomes > synaptosomes > myelin > mitochondria. The radioactivity present in the retina and in the optic pathway was exclusively localized in the PtdIns during the whole time interval studied. Ten days after the precursor injection, a high portion of the radioactivity transported was detected in the water‐soluble pool, separated from the ON and OT, whereas no significant counts in the corresponding LGB and SC pool were found. The kinetics of PtdIns labeling, observed in the different optic components, indicated a rapid axonal transport of the phospholipid; besides, the presence of labeled PtdIns in the purified myelin suggested a transaxonal migration of the phospholipid and its free precursor.
Published Version
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