Retinal pigment epithelial cells (RPE) actively retrieve and recycle docosa
hexaenoic acid (DHA, 22:6n-3) from phagosomal phospholipids back to photore
ceptor cells. Here we studied the fate of DHA in primary culture rat RPE ce
lls after feeding with a suspension of rod outer segments (ROS) for 4 hr, P
hospholipids (PLs), triacylglycerols (TAG), and free fatty acids were isola
ted from cells and media by thin layer chromatography (TLC), and their acyl
groups quantified by gas liquid chromatography (GLC). In RPE cells, DHA-PL
s increased 3.5-fold by 4 hr, decreasing thereafter to 1.6-fold above basal
by 24 hr, In contrast,18:1-PLs were decreased by 13%-18% below RPE basal v
alues by 8-24 hr, respectively, DHA-TAG showed the highest increase (21-fol
d) by 8 hr. Free DHA displayed a small increase in the cells with a prefere
ntial release and accumulation into the media by 24 hr. These results show
that in rat RPE cells, photoreceptor cell DHA is transiently incorporated i
nto TAG prior to its release and uptake into 18:1-PLs, These metabolic path
ways and remodeling may be critical in the conservation of this essential,
photoreceptor cell fatty acid. (C) 1999 Wiley-Liss, Inc.