title: A freeze-fracture evidence for lateral expansion of the plasma membrane of rat retinal pigment epithelial cells.
abstract: Distribution of the membrane particles of the retinal pigment epithelial cells of Wistar rats was studied by using freeze-fracture replicas. The overall view of the basal surfaces shows a mosaic pattern owing to membrane infoldings and interdigitated cell margins, where the P-face particles are as dense as 4.4 x 10(3)/micron2 and many particle-free patches can be seen on the basal membranes infolded into the cytoplasm. The particles of the lateral membrane are packed most closely as 6.7 x 10(3)/micron2 through the plasma membrane of the cell, where elaborate junctional complexes are seen surrounding the cell. In particular, on the side-junctional zone of the lateral membrane, they are counted as 7.7 x 10(3)/micron2, while the number of particles on the basolateral membrane is 5.5 x 10(3)/micron2. On the apical membrane the density of particles is 4.9 x 10(3)/micron2 and it is as many as on the basal membrane. Such a decreasing gradient of the distribution of the particles from the lateral to the basal or apical membrane is discussed with respect to their function.
mesh_terms: D000818:Animals; D002462:Cell Membrane / Q000648:ultrastructure; D005614:Freeze Fracturing / Q000295:instrumentation / Q000379:methods*; D008854:Microscopy, Electron; D010857:Pigment Epithelium of Eye / Q000648:ultrastructure*; D051381:Rats