Dietary omega-3 fatty acids and accumulation of docosahexaenoic acid in rod photoreceptor cells of the retina and at synapses.

Docosahexaenoic acid (DHA), the major biosynthetic product of the omega-3 family of fatty acids, is uniquely concentrated in the retina and synaptic membranes. In the perinatal period of life, when the bulk of synaptogenesis and photoreceptor biogenesis takes place, large requirements of DHA may be met first by the placenta and then by maternal milk. Linolenic acid (LLA), the precursor of DHA, is the most prevalent fatty acid of the omega-3 series in the stomach contents of newborn mice. In this study we have investigated the fate of radiolabeled LLA and DHA injected intraperitoneally in developing postnatal mouse. Our results show that radiolabeled LLA was taken up by the liver and DHA was synthesized; at 72 hrs post-injection about 90% of the label had been converted to DHA. Since there was a time-dependent buildup of radiolabeled DHA in blood plasma with negligible early uptake of LLA by the brain and retina, we hypothesize that the liver may secrete lipoproteins containing DHA and that this process is regulated by the nervous tissue.