Lipids of the retinal pigment epithelium in RCS dystrophic and normal rats.

The lipid composition of retinal pigment epithelial cells was determined for normal cells which have full phagocytic ability and for a genetic variant with impaired phagocytic function. Retinal pigment epithelial cells from 9-14-day-old congenic strains of normal (RCS-rdy+) and dystrophic (RCS-rdy/rdy) rats were separated from intact retinas and homogenized in 0.08 M Tris base, pH 7.4. The lipids were extracted using 2:1 chloroform--methanol. Fatty-acid methyl esters identified by gas chromatography were: 16:0, 17:0, 18:0, 18:1, 18:2 omega 6, 20:0, 20:2, 22:0, 20:4 omega 6, 22:4, 22:5, 22:6 omega 3. Major fatty acids for both normal and dystrophic cells were: 16:0, 18:0, 20:4 omega 6, 22:6 omega 3. One- and two-dimensional thin-layer chromatography was used to determine phospholipid composition of pigment epithelial cells at two different age groups. The relative amount of phosphatidylethanolamine was significantly higher in dystrophic RPE cells compared with normal cells (20.7% for 9-11-day-old and 17.3% for 12-14-day-old dystrophic rats). Cells from normal animals contained a higher level of phosphatidylethanolamine in the older age group whereas RPE cells from dystrophic animals contained a lower level of phosphatidylcholine in the older group. Anomalous phospholipid composition of dystrophic pigment epithelial cells may be associated with a change in cellular membranes and a defect in the cellular processes involved in phagocytic function.