Nonmembrane associated dolichol in rat liver

The distribution of dolichol in rat liver was studied. Upon high-speed centrifugation, 9% of the total tissue dolichol was recovered in the supernatant. Dolichol was enclosed in vesicles and in lipidic particles which were isolated by gel filtration and density gradient centrifugation. The particles had a diameter of 20 nm and contained dolichol, ubiquinone, cholesterol, phospholipid and some protein. Similar particles were recovered upon incubation of isolated hepatocytes with liposomes containing dolichol. From the lysosomal lumen, lipid particles containing dolichol, ubiquinone, cholesterol and phospholipid, but no protein, were isolated. The diameter of the particles was 20-40 nm with a molecular weight of 130 kDa. Puromycin treatment inhibited protein synthesis, but did not affect dolichol transfer from the endoplasmic reticulum to lysosomes, suggesting that the transfer is not mediated by newly synthesized apoprotein. The results indicate that a sizeable portion of the total cellular dolichol is present in cytoplasm and in lysosomal lumen. Furthermore, dolichol probably participates in the translocation process.