Selective phagocytosis of liposomes by cultured RCS rat pigment epithelium

Liposomes 0.5 to 5 micron in diameter and of various phospholipid compositions were used as a simplified model of rod outer segment membranes to examine the phagocytic mechanism of cultured explants of retinal dystrophic Royal College of Surgeons (RCS) and normal Long-Evans (LE) rat pigment epithelium. RCS pigment epithelium explants phagocytized liposomes composed of phosphatidylserine (pS) plus phosphatidylinositol (pI). However, phagocytosis was not observed in RCS pigment epithelium explants incubated with liposomes composed of phosphatidylcholine (pC) plus phosphatidylserine (pS), phosphatidylethanolamine (pE) plus phosphatidylinositol (pI), or pC + pS + pI + pE. Normal LE pigment epithelium explants phagocytized all preparations of liposomes. The ability of RCS pigment epithelium to differently phagocytize liposomes preparations of different phospholipid composition supports the idea that phospholipids in the membrane may participate in the phagocytic mechanism.