Expression of @entity3913 receptors for pinocytosis and phagocytosis on XXXX retinal pigment epithelium.

@entity1 @entity575 @entity1713 @entity3913 @entity35
We report here the presence of a @entity3913 -specific receptor on apical membranes of @entity35 retinal pigment epithelial (RPE) cells. For pinocytic studies, 125I- @entity3913 -BSA (125I- @entity1 -BSA) was incubated with RPE explants from normal (Long Evans) and dystrophic (pigmented RCS) @entity35 retinas. Normal RPE bound 36.1 ng of ligand and, in the presence of mannan competitor, the amount bound was 18.3 ng. In a similar assay, total ligand uptake by @entity1713 was 25.9 ng with 9.8 ng specific for @entity3913 recognition. Comparing the amounts of ligand bound, @entity1713 recognized 55% of the amount recognized by normal RPE. The presence of the @entity3913 receptor was localized on both normal and @entity1713 apical plasma membranes by autoradiographic techniques using 125I- @entity1 -BSA. Normal RPE showed a greater number of @entity575 grains present at the apical cell membrane as compared to @entity1713 . @entity575 grains were significantly reduced when incubation with the ligand was carried out in the presence of a mannan competitor. Further, in phagocytic studies, latex beads coated with mannan were used as phagocytic particles. Normal RPE phagocytized 4.52 mannan-beads per cell profile by a @entity3913 -specific mechanism, whereas @entity1713 did not recognize mannan-beads. Our data suggest that RPE cells express surface receptors which recognize both soluble and particulate @entity3913 ligands. The pinocytic and autoradiographic studies suggest that normal RPE binds more soluble ligand than does @entity1713 . If the @entity3913 receptors mediate both pinocytosis and phagocytosis, a possible reduction in number of soluble @entity3913 binding sites on the @entity1713 may be related to the diminished phagocytic recognition of particulate ligand by the @entity1713 .(ABSTRACT TRUNCATED AT 250 WORDS)
